Introduction: Sliding Puzzle Secret Compartment Table

The Sliding Puzzle Secret Compartment Table is an idea that I have been tossing around for some time.  I have always enjoyed Puzzles, Woodworking, and Secret Compartments and this project combines the three in a fun and interesting way. The idea behind the table is that it conceals a secret compartment that can only be opened when the sliding tiles on the table top have been aligned in just the right way, otherwise the secret compartment remains locked shut. Along with the sliding tile hidden compartment the table also conceals a false bottom compartment and a secret drawer hidden in the apron under the bottom shelf  which requires a special magnetic key to open.

This Instructable will cover each step of the build from the design phase, to building the sliding tile mechanism, to applying the last coat of finish.  I have tried my best to document each step and to provide any hints and tips that I may have learned through the build process so that you can hopefully follow these instructions to build a Sliding Tile Secret Compartment Table of your own. Enjoy!!

General Information about this project:
  • Table Dimensions: 33" Tall  X  30" Long  X  30" Wide 
  • Number of Compartments Concealed: 3
    • Compartment 1: The compartment accessed by successfully aligning the sliding tile puzzle
    • Compartment 2: The compartment located under the false bottom in compartment 1
    • Compartment 3: A secret drawer hidden in the apron of the bottom shelf
  • Estimated Build time: 1 Month working after work and on weekends
  • Estimated Cost: $150-$200 Depending on what materials you already have.
  • Skills Required: Intermediate to advanced wood working knowledge and the ability to measure very accurately.
 9 Reasons why you should make this project:
  1. It's fun to make and fun to play with.
  2. Everyone likes puzzles.
  3. Because it is actually pretty easy to build despite the fact that it looks very complicated.
  4. In building this table you will learn tricks and techniques that might be useful in future projects.
  5. Because you'll learn how to build several cool jigs that might be useful in future wood working projects.
  6. It would be a great addition to your home i.e. it looks nice.
  7. Because secret compartments are cool and this table has 3 of them which makes it extra cool
  8. Because you would pay twice as much to buy a table that wouldn't do ten percent of the cool things this one will.
  9. Because if you're like me, any reason to be in your workshop is a good reason!

Step 1: Tools and Materials

This project requires a few more tools than many of the Instructables I have published in the past but if you have a table saw and some basic wood working tools you should be able to tackle it without much of a problem.  As for materials your major costs are going to be in the wood and plywood needed for this build.  In total I spent right around 120 dollars on materials but I also salvaged many of my supplies such as hinges and table legs and I had a lot of the required materials from previous projects. If you were to buy everything needed to build this table from a home improvement store such as Lowe's or Home Depot the supplies needed for this build would cost roughly 200 - 225 dollars. Consult the list below to see the materials needed for this project and their associated costs and don't forget to read the blurb under the list for some ideas on how to cut costs if your interested in building this table but would like to save a little money in the process.

  • 3/4" Plywood Sheet (4' X 8') $55 - Available at home improvement stores like Lowes and Home Depot.  You'll be able to get most of your table parts out of this sheet. 
  • 1/2" Plywood Sheet (4'X4') $25 - Also Available at home improvement stores.  You'll be cutting this into four  2' X 2' sections to create the floor the tiles slide on, secret compartment bottoms, and the bottom of the  hidden drawer.
  • 1/4" Plywood Sheet 2'X2') $5 - Used to create the raised numbers that adorn the tiles.
  • Hard Wood Boards ( 1" X 4" X 8') $14 - Used for making trim, I used red oak because I selected oak plywood to build my table.
  • Table Legs $25 - I salvaged the table legs used for this project from an old maple table. I was able to cut the legs down into 1.5"X1.5"X28" lengths which was exactly what I needed for this build. If you can't find legs to salvage you can purchase pre-made table legs from home improvement stores and from
  • 3 Maglocks $15 - I used Dream Baby Mag Locks which are intended for childproofing cabinets but work amazingly well for creating secret magnetic compartments that are completely undetectable.  you can find a pack of 4 Mag Locks on for about 15 dollars.
  • Three 3/4" X 1/16" Neodymium Magnets $7 - These will be what trigger the Mag Locks to open the secret compartments.  The magnets will be installed in the bottoms of the sliding titles in key locations so that when the tiles are in the proper places the secret compartment will be able to open. Magnets will also be used to create a special magnetic key to open the secret drawer hidden in the apron of the table shelf.
  • Hinges $12 - The type of hinges I used for this build were Richelieu Frameless Cabinet Hinges.  These are the perfect hinges for a secret compartment build as there are concealed within the compartment so you don't have to worry about the giveaway of having visible hinges on your secret compartment.
  • Drawer Slides $20 - Used for mounting the secret drawer in the shelf apron. 
  • Wood Glue $3 - I use Tite Bond Original Wood Glue which is available at home improvement stores like Lowes and Home Depot.
  • 2 Butt Hinges $3 - Used for creating the hinged joint that allows the false bottom to fold up so that it can be removed.
  • 5 Minute Epoxy $3 - Used to glue the neodymium magnets into the bottoms of the sliding tiles.
  • Screws $4 - No real size/length requirements here, simply use the type of fastener that is best suited for the task at hand. For this project I bought a 500 piece variety pack of screws from Harbor Freight which served me well.
  • Wood Filler $6 - For filling any gaps or dents in the table and for creating the bevel on the numbers that adorn the sliding tiles.
  • Wood Trim $8- Used to conceal unsightly exposed plywood edges. Available from Lowes or Home Depot, or if you have access to a router you can custom make your own.
  • Wood Stain and Polyurethane $12- My chosen methods of finishing wooden projects, you could however paint, shellac, or oil finish your table.  One of the great things about wood working is the multitude of finishes that can be applied to enhance the natural beauty of the wood.
  • Wood Biscuits $10 - These aren't necessary but if you have access to a biscuit joiner they are pretty useful as they add a lot of strength when gluing the different table parts together.

Note that many of these materials can be acquired for far less money then it would cost to buy them from the store.  Hinges, Table Legs, Drawer Slides and Even Wooden Trim can all be salvaged from inexpensive flea market or thrift store furniture for a fraction of the in store cost and only a small investment of time. Most of the materials I had on hand were salvaged from furniture that students threw away last year when the local college let out for the summer break.

: You can complete this build without many of the tools listed below.  Tools like the Scroll Saw and Router were used for decorative details and depending on how you wish to make your version of this table they may not be needed.  Tools that are absolutely necessary for this build will be marked with a *.

  • *Table Saw equipped with a standard 1/8" kerf blade
  • Masking Tape
  • *220 Grit Sand Paper
  • 400 Grit Sand Paper
  • Wood Chisels
  • Utility Knife
  • Scroll Saw
  • Band Saw
  • *Small and Large Wood Clamps
  • Paint Brushes
  • Carbon Paper
  • Router or Router Table (Used to make custom trim; optional but useful)
  • Biscuit Joiner (Optional but useful)
  • *Hand Drill
  • Countersinking Drill Bit
  • *3/4" Forstner Drill Bit
  • *1-3/8" Forstner Drill Bit
  • *Phillips Driver Bit
  • *Tape Measure
  • *Compound Square AKA Tri-Square - (One of my favorite tools, I used this tool at least 100 times on this build doing everything from measuring parts to setting blade height and fence distance on my table saw.  If you don't already own one of these I highly suggest picking one up asap.)

Step 2: Design

Design was a big factor for this project.  before I started working I had to consider issues like the aesthetic of the table as well as technical issues such as how to get the sliding tile mechanism to activate the locks that hold the table's secret compartment shut.  I worked through these issues by creating a variety of sketches and when I felt that I had a good understanding of where I wanted the project to go I set about creating 3D models of the Sliding Tile Secret Compartment Table using a program called Sketch Up from Google.

Modeling the table was extremely beneficial. The 3D models I created allowed me to experiment and make changes to my project so that I wouldn't have to waste time and materials testing things in real life.  The models also gave me a good sense of what the finished project was going to look like and best of all I was able to build the table to scale in Sketch Up meaning that when the model was complete I was able to use measurements from it to cut the parts I needed to build the actual table.

Check out the pictures in this step for some insight into the design process and to get an idea of how the table functions.

Something else worth noting as it relates to design is the way in which the table was assembled.  Basically I started ths project by making the sliding tiles and then built everything else based on their dimensions.  As such, this instructable starts by showing you how to make the tiles.  Once the tiles are constructed the way in which to approach the other steps can vary, for example you can build the bottom shelf and hidden drawer at any point during table construction.  In some steps you may notice that parts of the table have been built that haven't yet been discussed, this is because I jumped forward in the build while waiting for things like parts to arrive or glue to dry. Don't worry if you see a step where something is done slightly out of order, that part of the build is most likely covered in a later step.

Step 3: A Word on Mag Locks

Before we get into the process of building the table, it's worth taking a second to talk about Mag Locks.  Mag Locks are what lock the secret compartments closed on the Sliding Tile Secret Compartment Table.  The idea is pretty simple but it's worth explaining as it will shed light on why I built things the way I did.  Basically Mag Locks consist of three parts, a magnet that works like a key to release the lock, the locking mechanism, and the catch that the lock catches on to keep the compartment locked shut.  

What makes Mag Locks so great for hidden compartments is that they are completely invisible when installed so anyone inspecting the table will have no idea what the mechanism is for opening the secret compartment or that there is even a secret compartment in the first place.  Also they use magnets and I think we can all agree that anything actuated by magnets is pretty darn cool.

The Mag Locks will be used in two ways on the Sliding Tile Secret Compartment Table.  The first way has to deal with the sliding tile mechanism; magnets will be installed in the underside of two of the tiles and Mag Locks will be installed on the underside of the floor the tiles slide on.  When the tiles with magnets slide into position above the Mag Locks the Mag Locks will disengage allowing the secret compartment to open.
The Second way the Mag Locks will be use will be to lock the secret drawer hidden in the shelf apron.  The installation for the drawer lock will be similar to how the Mag Locks are met to be used to lock cabinets, as such the drawer will need a special magnetic key in order to open.

Check out the include pictures to see the different parts of the Mag Locks and a few examples of them in action on the finished table.

Step 4: Cutting the Parts

The first step in making the Sliding Tile Secret Compartment Table is to cut out all of the pieces you will need from your 3/4" and 1/2" plywood.  Included in the step are diagrams of the different parts you will need with an example of how you can cut them from your plywood to efficiently use both sheets.

These are the same cut schematics I used when building my table and I'm happy to report that everything went together with no trouble and I still had a sizable piece of the 3/4" plywood left over for future projects.  With most wood working projects I'm a cut as you go kind of guy, but for larger projects like this I like to plan everything out so that I can make the most out of my time and materials.  

Step 5: Making the Tiles Part 1

Once all of the table parts have been cut out, the next step is to make the Sliding Tiles.

What is a Sliding Tile Puzzle?
A Sliding Tile Puzzle, also known as a 15-puzzle is a puzzle that consists of a frame of numbered square tiles in random order with one tile missing.  The goal of the puzzle is to return the tiles to the correct order by sliding tiles into new positions via the open space left by the one missing tile.  Although the 15 piece puzzle is the norm, there are also 8 piece and 24 piece variations for this classic puzzle.
How the Tiles Work
The trick to making a sliding tile puzzle is all in the tongues and grooves that are cut on the edges of the tiles.  Each tile has four edges, two of which are cut with tongues and two that are cut with grooves.  Note that the tongues and grooves are cut on adjacent sides (sides connected by a corner) and not on parallel sides, (so if you refer to the example you can see that the top and left sides of the tile have tongues and the bottom and right sides of the tile have grooves.  By cutting the tiles in this way they will be able to slide both up and down and left and right when they are installed into the frame, just like the small plastic sliding puzzles that you may have played with as a kid.

For the Sliding Tile Secret Compartment Table you will need to create 15 sliding tiles from the 6" tile blanks that were cut from the sheet of 3/4" plywood in step 4. Continue on to steps 6 and 7 to learn how to cut the tongues and grooves using a table saw and a standard 1/8" kerf saw blade.

Step 6: Making the Tiles Part 2: Cutting the Tongues

The real trick to making the tiles slide smoothly is in properly setting up your table saw for each cut.  To make the tongues start by setting your blade height to 1/4" and set your table saw fence so that the distance from the outside edge of the saw blade to the fence equals 1/2".  With everything set correctly the next step is to make cuts into the front and back faces of the tiles on adjacent sides; these cuts will define the length and thickness of the tongues and will also define the size of the tile face reducing it from 6"X 6" to 5.5"X 5.5".  Once you've made these cuts on the fronts and backs of all 15 tiles you will need to reset your saw to finish cutting the tongues.

This time set the saw so the blade height is 1/2" and so the distance from the inside edge of the blade to the fence is 5/8".  With everything set correctly run your tiles through again, only this time stand them vertical against the tafence so that when the blade cuts into the wood it meets the cuts you made previously.  As before you will need to make this cut 4 times to each tile, twice on the front and twice on the back, to establish the thickness of the tongues, which if you have set your saw correctly  should be 1/4" thick.

If this explanation is a bit hard to follow consult the cut diagram included in this step for a visual of how the saw should be set up to make the tongue cuts.

Once you have all of the tile tongues cut continue on to the next step to learn about cutting grooves.

Step 7: Making the Tiles Part 3: Cutting the Grooves

Cutting the grooves is easier than cutting the tongues and requires you to set your table saw only one time.  for the groove cuts your saw blade height needs to be set slightly over 1/2" and your fence needs to be set 1/4" from the inside edge of the saw blade (the inside edge of the saw blade is the edge closest to the face of the table saw fence).  With everything set the next step is to run your tiles vertically along the fence so that the blade cuts into the edges that do not have tongues cut on them.  To create grooves that are wide enough to fit the 1/4" thick tongues you will have to flip your tile over horizontally and re-cut them so that the two cuts come together to make one large groove.

Tip: The reason that you set the saw blade slightly above 1/2" is to give the tongues a bit of extra clearance as they slide through the grooves.  You can see examples of this in the pictures on this step.

Tip: Test the fit of the tongues and grooves on the first tile you cut grooves into.  If the tongue is tight within the groove it is much easier to fix the problem now as opposed to finding out the tongues and grooves are to tight after you have cut grooves into all fifteen tiles.  If the fit is to tight simply move your fence slightly closer to the blade and make the cuts on both sides as before. Moving the table saw fence closer to the blade will lessen the amount of wood on either side of the grooves thereby making the grooves wider which will in turn give the tongues more clearance to slide through them.

Step 8: Decorating the Tiles

Although there are countless ways to decorate the sliding tiles, from a picture that spans all the tiles, to painted on designs, I decided on a traditional approach where the tiles would be numbered 1 - 15, and instead of a flat painted on numbers I opted for a raised design by cutting the numbers from  pieces of 1/4" plywood.  Decorating the tiles in this way consisted of 4 steps, making the numbers, attaching the numbers to the tiles,  applying wood filler and sanding, and painting and finishing.
  1. Making the Numbers: To make the numbers I started by creating a word document with the numbers 0-9 typed in French Script MT font at a size that would properly fit onto the tiles.  I then printed the document and used carbon paper to trace the numbers onto pieces of 1/4" thick plywood. Note that I had to trace several of the numbers more than one time, for example I needed eight number 1's to create the the numbers 1-15. Once I had all the numbers traced onto the 1/4" plywood I went to work cutting each number out with my scroll saw.  When all the numbers were cut out I sanded them to remove any rough spots created during cutting.
  2. Attaching The Numbers to the Tiles: Once the numbers had been cut out and sanded  I affixed them to the tiles using wood glue. Note, make sure that you glue the numbers to the tiles in the correct orientation, the tiles only fit into each other and into the frame one way so if you don't pay attention you might end up with a few tiles that look like they are upside down or turned 90 degrees because the numbers were glued on incorrectly. 
  3. Applying Wood Filler and Sanding:After the glue has cured the next step is to use wood filler to create a bevel where the edges of the numbers meet the faces of the tiles.  The wood filler bevels are purely aesthetic but they do make the tiles look nicer as the flowing transition of the wood filler bevel looks more intention than the stuck on look of simply gluing the numbers in place.  Once you've coated all the number edges with wood filler use your finger and a bit of water to smooth the wood filler so the all the bevels look even, then remove excess wood filler and allow the filler to dry and set.  When the wood filler has finished drying, give everything a good sanding to even out the surfaces in preparation for painting.
  4. Painting and Finishing.  Painting was pretty straight forward, Using acrylic paint I painted the faces and edges of each tile one solid color. Half of the tiles were painted white and half green so that the colors alternated creating a checkerboard pattern.  Once the first coat of paint was dry I highlighted the numbers on green tiles with white paint and the numbers on white tiles with green paint.  Lastly I finished each tile with 3 coats of spray semi-gloss polyurethane. 

Step 9: Making the Sliding Tile Frame Step 1 Assembling the Frame

Once you have your tiles finished the next step is to make the frame that holds them in place.  Making the frame is very similar to making the tiles in that you will need 2 of the frame pieces to have tongues and 2 of the frame pieces to have grooves.   These tongues are grooves are exactly the same as the ones that were cut on the tiles so follow the table saw set up diagrams from steps 6 and 7 to make the necessary cuts.
Once you have the tongues and grooves cut on the frame pieces the next step is to measure the frame pieces so that they are the right size to hold the tiles, and then to miter the corners of the frame pieces at 45 degree angles in preparation for assembling the frame and gluing it together.

Because each tile has a 5.5" square face the inside edge of the mitered frame pieces needs to measure 22". (4 tiles across multiplied by 5.5" per tile = 22")  Because the tiles will be moving within the frame it is advised that you add 1/16" to 1/8" to your measurements to give the tiles a little wiggle room, so instead of cutting your miters so the inside edge of frame pieces equals exactly 22", you may want to cut them so the inside edges measure something like 22 and 1/8".  Miter all four frame pieces exactly the same length so when they are put together to form the frame you'll end up with a perfect square.

With the frame parts cut the next step is to start putting everything together.  Start by gluing together 3 of your frame pieces leaving one frame piece unglued so that you can install the sliding tiles.  (Installing the tiles and attaching the last frame piece will actually be one of the last steps of this build so it is very important that you do not glue the last frame piece in place right now, instead use tape to hold it in place to make sure the other three frame piece dry at the correct angles.)

Step 10: Making the Sliding Tile Frame Step 2 Attaching the Frame Bottom

With 3 of the frame pieces glued together and the forth piece taped in place the next step is to install the floor that the sliding tiles will slide across.  This floor is made from one of the 2'X 2' squares of 1/2" plywood that was cut during step 4.  Because the inside area of the frame measures 22"X 22" and the 1/2" plywood square measures 24"X 24" you will be able to overlap the plywood square over the frame 1" on all sides for attachment purposes.  Line up the 1/2" plywood square so that it overlaps the four frame pieces equally and then use wood screws to affix the 1/2" plywood square to the three glued frame pieces remembering not to screw the unglued frame piece into place.

At this point you can put your tiles into the frame to test how they slide past one another. Simply un-tape the loose frame piece, install the tiles into the frame and tape the loose piece back in place. If everything works well then you are ready to move on to the next step.

Step 11: Making the Table Body and Legs

Alright If your building along then you should be happy to have reached this step as building the table top and sliding mechanism is definitely the hardest part of this project.  From here on out everything is basic wood working with only a few small twists thrown in for the secret compartments hidden underneath the table top and inside the apron of the bottom shelf.  Use the included pictures and captions to construct the body of your table and reference the information below for information regarding what parts will be needed for this step:

Parts Needed:
4 Table Aprons
4 Table Legs
3 Shelf Aprons

The easiest way to build the table body is to create two sub-assemblies and then to connect those sub-assemblies to make the table body.  Each sub-assembly is essentially one side of the table that has been glued and biscuit jointed together, i.e. two legs with an apron fixed in place at the top and a shelf apron fixed in place a few inches up from the bottom of the legs.
Once you've created two of the sub-assemblies, the next step is to connect the two sub-assemblies using the 2 remaining aprons and the one remaining shelf apron (we're only using one shelf apron here because the other shelf apron will become the front of the hidden drawer in a later step.)  Once everything is biscuit jointed and glued together use bar clamps to hold everything in place until the wood glue has dried.

Step 12: Attaching the Table Top to the Table Body

With the table body complete, now is a good time to attach the table top.  How you attach the table top to the body of the table will largely depend on the type of hinges you choose to use.  For my table I chose to use Richelieu frame-less cabinet hinges".  These hinges are nice for several reasons, first and foremost the are well built and designed to to distribute the weight of the table top better then something like  traditional butt hinges or piano hinges.  Secondly, they are designed in such a way that the hinges are completely hidden when the compartment is closed, meaning that you don't have the tell-tell barrel of a hinge sticking out from under your table top tipping people off to the fact that there may be a secret compartment hidden underneath. Lastly these hinges lift the table top up and backwards so the table top doesn't jam against the table body when the secret compartment is open.  As for installing the hinges I suggest you follow the instructions that your hinges come with and remember that hinge installation can be tricky business so it is always a good idea to test how your going to install your hinges with some scrap wood before you decide to install them into your actual piece of furniture.

Note: In later steps you will notice that the tops of the table legs have been chamfered (angled) so that they are thinner near the top.  This was because the table top was jamming against the table legs which was preventing the table top secret compartment from opening. Although this wasn't planned it was necessary and reminded me of something one of my favorite teachers use to say, "The mark of a good craftsman is not in how many mistakes they make, for even the best craftsman makes mistakes, instead, it is in how they recover once a mistake has been made."

Step 13: Making the Secret Compartment True Bottom and False Bottom

With the body of of the table built and the table top and hinges installed, the next step is to make the actual bottom of the secret compartment (the true bottom), and the false bottom of the secret compartment.  Both bottoms are made exactly the same way and both are held in place with wooden spacers that will also be made in this step.
The true bottom and false bottom are both start out the same way. Both bottoms are made from the 2' X 2' squares of 1/2" plywood that were cut back in step 4.  The space inside the secret compartment is exactly 2' X 2' so the 2' X 2' squares of 1/2" plywood will fit perfectly into place.
True Bottom
Not much needs to be done to the true bottom of the secret compartment. All you have to do is drill a hole roughly in the center of the 2'X 2' square that is about 4" back from the front edge, check out the picture for an example.
The False Bottom
As you can see in some of the pictures and in the video on the first step, the false bottom is secretly hinged so that it can fold up to be removed revealing the secret compartment hidden underneath.  To do this start by cutting the secret bottom into two pieces with 1 of the pieces being roughly 4" wide as shown in the picture.  Next position the two pieces back together and install hinges onto what will become the underside of the false bottom.  You could do these steps before or after applying finish to the false bottom but I recommend waiting until after you have applied finish as the finish will lay nicer across the uncut plywood and will therefore make a near invisible seem once cut.
Making the Spacers
The spacers serve three functions, they are what hold the true bottom of the secret compartment in place, they determine the size of the compartment underneath the false bottom, and hold the false bottom in place.  When making the spacers you need to consider how large you want the compartment hidden under the false bottom to be.  The trick is that you want the space to be large enough to store things, but not so large that the placement of the false bottom looks suspicious.  For my table I made the spacers 1.5" tall which was tall enough to store a variety of items but not so tall that it made the height of the false bottom look conspicuously out of place.

Attach the spacers on all four sides of the inside of the secret compartment so that the bottoms of the spacers sit 1/2" up from the bottom edges of the aprons.  The reason you want the spacers 1/2" up from the bottom edges of the aprons is that you will be attaching the true bottom to the underside of the spacers and you don't want the true bottom hanging out below the edge of the aprons, so recessing the spacers 1/2" gives you room to install the true bottom up inside the compartment created by the aprons.

When the spacers have been attached you are basically ready to install the true and false bottoms, however, I advise waiting until later to install the two bottoms as they are easier to stain and finish before they are installed into the table.  When it is time to install the bottoms, the true bottom will be installed by screwing it to the underside of the spacers, and the false bottom will simply set on top of the spacers where it can be easily dislodged to gain access to the compartment hidden below.

Step 14: Building the Hidden Drawer

How the Hidden Drawer Works:
The idea behind the hidden draw is that the front of the draw looks like part of the apron that sits underneath the shelf  so that the drawer is essentially invisible to the unsuspecting person.  The drawer will be locked shut via a Mag Lock that can only be opened by using a magnetic key in just the right spot to release the lock thereby granting access to the drawer and it's contents. Note that you will be making the magnetic key in a later step.

Building the Drawer
Building the drawer is very much like building a shallow box.  Reference the cut diagram from step 4 to find the measurements for the drawer components and follow the pictures to see how the drawer is assembled. Note that the drawer is composed of just five parts, a front that is the shelf apron piece that we didn't install back when the table body was assembled, a back, two sides, and a bottom. Build the drawer so that there is a 1/2" gap on either side of the drawer between it and the shelf apron pieces that have already been glued into place on the table body.  These gaps will be used to install drawer slides that will hold the drawer in place and will also allow it to be easily opened and closed. (Note the 1/2" gap is based on the drawer slides that I suggest in the materials list on step 1, different drawer slides require different amounts of clearance so make sure that you build your drawer based on the hardware that you're going to use.)

Also note that the drawer bottom is one of the 2' X 2' pieces of 1/2" plywood that was cut back in step 4.  You will need to alter the dimensions of this piece of plywood so that it fits within the confines of your drawer. For my drawer I used a technique for installing the drawer bottom  known as the captive bottom method, for this method I cut  1/4" deep dados that were 1/2" wide in the front, back, and sides of the drawer and then installed the drawer bottom within the dados.  For this method of installation I had to cut the drawer bottom to a side of 23.5" X 23.5".
Installing the Drawer
Installing the drawer is pretty straight forward and your drawer slides should come with directions that will instruct you on how to properly install them and mount them to the drawer.  The big thing you want to remember when installing the hidden drawer is that the front of the drawer (the shelf apron) has to be situated at the same height as the other shelf aprons so that the shelf sits evenly once it is installed. 

Step 15: Cutting the Shelf Top

With the hidden drawer built and installed, the next step is to build the shelf top that the drawer will be hidden under.  The shelf top is a piece of 3/4" plywood that has been cut into a 28" X 28" square.  installing the shelf takes a bit of work as the corners of the shelf have to be removed to make room for the table legs (see picture).  
Once you have the wood removed from the corners so that the shelf fits in place, the next step is to install the Mag Lock mechanism before gluing the shelf top into place.  (The reason you install the mag lock before gluing the shelf top down is that the mag lock catch needs to be installed onto the underside of the shelf which would be very hard to do with the shelf was glued in place.)  Continue on to the next step to learn about installing the hidden drawer Mag Lock.

Step 16: Installing the Hidden Drawer Mag Lock

Installing the Mag Lock in the hidden drawer looks pretty complicated but it's actually pretty simple.  Basically the Mag Lock gets installed on the inside of the drawer front and the Mag Lock catch gets installed on the underside of the shelf.  What makes the installation a bit tricky is that you don't have access to the inside of the drawer when it is pushed shut so you have to do a bit of work to figure out where the catch needs to be installed so that the the drawer locks shut when it is pushed the whole way in.  Follow the pictures and diagrams in this step to learn how to install the hidden drawer Mag Lock.

Step 17: Optional: Making the Mag Lock Key

To access the hidden drawer compartment you'll need some type of magnetic key to deactivate the Mag Lock.  The simplest solution is to keep a small magnet close by but it is much more fun to make a special key.  The key I chose to make looks like a normal block of wood but it has actually been cut and drilled to conceal a strong neodymium magnet that can be used to deactivate the Mag Lock and open the drawer.  Note that your key could be anything so long as the item you choose has enough space to conceal a magnet but if you'd like to learn how to make a key like the one I made check out the pictures and follow the steps listed below.
  1. Select your block of wood.  The wood I used to make the key came from an off cut of one of my table legs.  The only things you need to consider when picking your block of wood is that it is large enough to conceal the magnet you are installing, and that it is long enough to safely cut on your table saw.
  2. Using the table saw, cut a section from the end of the block of wood that is no more than 1/16" thick.
  3. Next use the table saw again to cut away any unnecessary length from your wooden block so that you end up with a block of wood that is roughly a cube.
  4. Then mark the center of the wooden block and use a drill bit that is the same size as your magnet to drill a hole that is just deep enough for the magnet to set in it without sticking above the surface of the wooden block.
  5. Install the magnet into the hole and apply wood glue on the wooden surface all around the magnet
  6. Position the 1/16" section you cut from the block of wood earlier over the side of the block the magnet is installed into and clamp it in place until the glue dries, (Note, do your best to line up grain patterns as this keep the wooden block from looking like it has been altered.
  7. Lastly, once the glue has dried, sand the block until there is no evidence that the magnet has been installed.

There are several reasons why I chose to build the magnetic key in this way.  First is that it is very inconspicuous, the key looks like a simple block of wood and would be quickly overlooked by someone trying to figure out the secrets of the table. Second, even if someone was to figure out that the wooden block was the key, they would still have the challenge of trying to figuring out which of the blocks 6 sides would work to deactivate the secret drawer Mack Lock, never minding the fact that they would have to find the location of the drawer front and the Mag Lock in the first place.  All of this adds up to create a secret compartment that is amazingly hard to figure out and gain access too.

Step 18: Making and Installing Trim

In this step we'll be giving the table a little personality.  Until this point the table has been fairly blocky with a lot of 90 degree angles and straight edges but now's the time to make it look like something you would be proud to have in your home.

How and where you apply trim is an aesthetic choice but I chose to install my trim in these locations:
  • On the edges of the table top to cover the exposed plywood edges.
  • On the bottoms of the aprons to change the straight edge of the apron into a gentle curving edge similar to the look of mission style furniture.
  • On the edges of the shelf to cover the exposed plywood edges.

The trim I used to cover the exposed plywood edges of the table top and shelf is pretty standard and is something that you can pick up an any home improvement store, it's known as 3/4" cove trim or 3/4" cove molding.  On the other hand the arched pieces I made to trim the bottoms of the aprons had to be custom made and the process for making these pieces was pretty interesting. Check out the pictures to see how that part of the trim was created.

Step 19: Installing Sliding Tile Mag Locks Part 1

At this point the table is very close to being done with only a few things left to do.  Until now the sliding tile table top has had no mechanism for locking shut which makes for a pretty poor secret compartment.  In this step we will start the process of creating the locking mechanism which will keep the table top locked in place until the tiles are arranged in the correct order.

To lock the table top shut we will be using Mag Locks just like the ones used for the hidden drawer. What makes the table top locks different from the drawer lock is that instead of using a special key to unlock the compartment, the locks on the table top will be deactivated when tiles with magnets installed in their bottoms are slid into place over top the mag locks.

Installing the locking mechanism is a pretty complicated process that involves transferring measurements between the table top, table body, and tiles to ensure that the Mag Locks and Mag Lock Catches line up correctly when the table top is closed.  Follow the pictures, diagrams and instructions found on this page to start the table top Mag Lock Installation.  Note that installing the Mag Locks that hold the table top closed is a two part process.  the first part of installation will be covered in this step and the second part will be covered after stain and finish have been applied to the table.

Step 20: Finishing (Sanding, Staining, and Applying Polyurethane

What finish you choose for your table largely depends on your preferences.  I like a simple two part finish where the first part is applying a wipe on stain such as Minwax Golden Oak, and the second part is to apply several layers of a top coat like polyurethane. Whatever finish you decide to use,  start the finishing process by giving the whole table a good sanding with 220 grit sand paper being mindful not to sand too much on the plywood as you can quickly sand right through the veneer.  After you've finished with the 220 grit you can move up to 400 grit if you like, or you can move straight to to the next step, (in my opinion 220 grit is fine enough for most projects but if you're looking for a more lustrous shine on your table you may want to take the extra time to sand with 400 grit.)  

Once you've finished sanding give the table a good wipe down with tack cloth to remove all of the dust from sanding in preparation for applying finish.  As for how you apply your finish that depends on what finish you choose to use.  for best results adhere to the instructions found on the particular finish you choose.

Step 21: Installing Sliding Tile Mag Locks Part 2

With the finishes applied and dried we can now move on to finishing the sliding tile locking mechanism.  the process for installing the locks is laid out in detail in the pictures on this step, but I'll lay out the basic process here to give a little clarity to the more detailed instruction found within the pictures.
  1. Start by installing all the tiles into the table top.
  2. Next tape the loose frame piece tightly in place.
  3. With the first two steps complete use a piece of scrap wood to prop the table top open so that you can work on the inside of the secret compartment.
  4. Use the Mag Lock templates to mark the locations where the catch screws will go on the catch spacers.
  5. Once the catch screw locations have been marked, peel the adhesive backing from the template and close the table top. The adhesive will cause the template to transfer to the underside of the table top providing perfect alignment as to where the Mag Lock mechanism should be installed.
  6. When the template was transfer to the table top it was also flipped over meaning that you should now see the diagram of the holes for installing the Mag Lock, mark the locations of those holes but don't install the Mag Lock just yet. Note you can also install the Mag Lock Catches onto the catch spacers at this point.
  7. Position tiles above the locations where the Mag Locks will be installed; I chose tiles 13 and 15 so that my table would open when the numbers were put in ascending order but you could choose other numbers if you'd like to make opening the compartment a bit trickier. The tiles you position over the Mag Locks will be the key tiles that will deactivate the Mag Locks allowing access to the secret compartment.
  8. With the key tiles in position over the Mag Locks use a very small drill bit to drill through the center hole of the Mag Lock mechanism templates, through the sliding tile floor, and into the bottoms of the tiles.  These holes will be used for aligning magnets that will be installed in the bottoms of the key tiles to the position of the Mag Locks.
  9. Now un-tape the loose frame piece and remove the two key tiles.  You can also install the Mag Lock mechanisms on the underside of the table top at this point.
  10. Flip the key tiles over so that you can see the small holes that were drilled in their bottoms. Using these holes as guides, use a 3/4" Forstner drill bit to drill a hole just deep enough to hold a 3/4" neodymium magnet flush with the bottom of the tile.
  11. Scratch up the sides and face of two neodymium magnets with sand paper. 
  12. Squirt some epoxy in the 3/4" holes and install the scratched magnets. The scratches made in the previous step will help the epoxy adhere to the magnets making for a stronger bond.
  13. Use clamps to hold the magnets in place while the epoxy cures.
  14. After the epoxy has cured, remove the clamps and re-install the tiles into the frame.  With the mag locks installed on the underside of the table, slide the key tiles over top of them to deactivate the locks granting access to the secret compartment.
  15. If everything works, the sliding tile locking mechanism is complete!
Alright, I know that was a bit of a complicated process but hopefully the instructions above combined with the pictures will make it fairly easy to follow.  With the sliding tile locking mechanism installed, there are only a few more simple things to do before this build is complete.  

Step 22: Putting It All Together

All right, home stretch time.  At this point basically everything is done and your Sliding Tile Secret Compartment table is all but ready to find a place of honor in your home.  Before you tote your table from your workshop to your house here's what is left to do:
  1. Install the Sliding Tiles
  2. Glue and screw the last piece of the tile frame in place
  3. Screw the true bottom of the main secret compartment in place
  4. Drop the false bottom of the main secret compartment in place
  5. Optional: Make and install a table top prop out of a piece of dowel to hold the table top open, giving you easier access to contents hidden under the false bottom.
  6. Optional: Buy or make a custom glass table top to protect the sliding tile puzzle from dust and damage. Having a glass table top adds a lot of utility to the table as it makes the surface of the table flat so that it can function just as a normal table would, and when you want to use the puzzle or access the secret compartments all you have to do is lift off the glass table top and you're good to go.

    A note on moving your table:  Although you have probably already flipped and moved your table several times during the building process, it is still worth the time to discuss how to properly  move it.  The first rule of moving tables is to never lift from the table top and that rule applies ten fold to the Sliding Tile Secret Compartment Table.  Instead, employ the help of a friend and together lift the table by holding onto the legs in order to move it to it's new home. 

Step 23: Finished Project

If you've made it this far then congratulations, your sliding tile secret compartment table is now ready to conceal your most valuable treasures and secrets.  I really hope you enjoyed this Instructable, it is by far the most involved project I have posted to Instructables and I really hope that it was fun to read and fairly easy to understand.  As I said in the first step, although this project looks difficult to make, it is actually not to bad, so long as you take the time to measure and cut precisely, so if you're interested in building your own mysterious sliding tile secret compartment table I hope you take the risk and give it a shot.  Thanks for checking out my Instructable and please feel free to leave any questions or comments in the comments section below, in fact I would love to hear your comments so don't be shy about posting.

Best Regards!

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