Solid Maple "Unseen Maze" Gift




In this Instructable I will explain how I made the "unseen maze" as a challenging gift for my brother last Christmas.

The maze is made from solid maple, and has a compartment inside that contains the real gift.  The compartment remains locked until the challenge is completed.

The goal is to have a marble travel through two separate mazes until the marble becomes the "key" to unlocking the not-so-secret compartment.  The challenge is that the maze is not visible from the outside, and one must use sound, gravity, and patience to complete....or go crazy.

It has been over 9 months since I gave this gift to my brother.  When asked how he's progressing, the answer is usually, "I'm not really sure if I am making progress, or just going backwards."

Hopefully he'll unlock it one day....

In the figures below, I show the CAD assembly I used as the design baseline (shown in transparent so you can see the internal maze), and the second figure is the finished (but not assembled) product.

Step 1: Model/Design the Maze

I'm an engineer by trade, but also by hobby.  It took me months to simply dream up this idea, but only 2 days to build the final product.

To ensure that the design would work, and also to work out the maze itself, I used CAD software to design the maze before cutting any wood. The maze is constructed from 7.5" x 7.5" x .75" square boards, stacked 4 high for a total of 3" height.

Shown in the figures are exploded views of the mazes, compartment area, and lock/key assembly.

There are two mazes included in this; one on top, and one on bottom.  The marble is inserted into the top maze via a hole in the top, then the marble must travel through the first maze, where the exit of the first maze (on top) is the entrance to the bottom maze.  Once the bottom maze is completed, the marble falls between what i call the lock and key.  The lock and key are two pieces of wood that are not otherwise connected without the marble--the marble completes the connection and allows the key to actuate the lock--unlocking the compartment.

Step 2: Getting to Cutting

A benefit of having computer models of the mazes was that I could print out the designs on a 1:1 scale and use the paper for measuring and checking my progress.  This also saved having to dimension and then redraw the complicated maze structures on the wood itself.

With the parts modeled and drawings printed I started with the smaller components first.

Step 3: Making the Key/Lock Assembly

The first two pieces are the key and the lock.

The piece that holds the compartment (next step) in place is what I call the lock. This is the shorter, more intricate piece.

The piece that can be pushed from outside of the assembly is what I call the key.  This is the longer piece.

Once I had cut the two pieces to length, I clamped them together and used a forstener bit and a drill press to bore the "keyhole"--where the marble will go to engage the lock.  This was a tricky item to get right the first time.  Using a spring clamp, I held the ends together.  I chose the forstener bit, because it was brand-new, sharp, and forsteners can cut partial-holes--so it worked.  After cutting the hole, I placed the marble inside to ensure a good fit.

After that, I turned the key on it's side (not shown) and used the same forstener bit and the drill press to cut a half-hole in the side.  This way the marble can come in right on top of the key, then fall in place between the key and lock.

The last thing I did to finish off the key was to drill a small hole, just over a 1/4" to loosely fit a cut dowel.  The hole is about halfway through the key's thickness.  With a spring behind the dowel, the dowel allows me to keep the key from falling out after assembly.  More on this later....

The lock was much more tricky to cut. It is short, and has the most detail. Naturally, there are no pictures of me creating this part, because I was too busy almost loosing a finger on my router table.  Be careful.

I still have all my digits.

Step 4: Making the Compartment

To make the compartment--or where the goodies go--I started with a long block.  I intentionally cut this piece longer than I needed so I could have an area to hold on to (or screw down) while using the router to cut the pocket and locking area.

I screwed the compartment down to my work bench to work the details.

I started this piece with a dado cut to start the locking area.  Then I used the router to cut the "teeth" where the lock (previous step) will mesh.  I used the lock heavily during this process to check the fit and clearances.

Once the teeth were cut, I hollowed out the pocket.  In my design, I had allotted for only 1/2" or so of depth since the material thickness is only 3/4".  Since the booty was Smarties, they almost didn't fit.  I had to re-cut this later on to fit the goodies inside.  Usually, I don't like taking wood to less than 1/4" thickness--but the whole point of this project was to hide Smarties inside....

Step 5: Making the Main Body

This part was where it started getting fun. Also frustrating.

The main body is made up of two 7.5" square boards of maple 3/4" thickness.  The router was used for this operation.  Lots of cutting.  I started with the track for the compartment area.  Shown in the first figure, under the red bar and clamps.  The next step was to cut the track for the key, a simple dado, then the area for the lock.

After a few passes, I got everything to fit. I even had to round off the edge of the lock to fit in the internal fillet left by the router.  It was tricky, but ended up nice--too bad it will never see the light of day again.

I tested the key/lock mechanism a few times to ensure they worked.  Reliability is important since it will probably take years before the marble finally gets into place.

The really frustrating part was where I had to reverse this, and cut the same pattern in the mating piece (the two body boards mate, with mirrored cut-outs to house the lock, key, and compartment). 

Measure a bunch, cut a bunch.

Step 6: Making the Maze(s)

This step is where having the 1:1 scale drawings printed out really helps.  Simply tape the paper to the block and trace all of the lines with an exacto-knife or other handy razor.

I was planning on free handing all of this cutting (via a router), so I also drew a line through the areas to cut out with a permanent marker.  I did this so that I would know which area to cut/not cut.

Step 7: Assembly

Now that all of the piece-parts are completed, it is time to assemble.

I wanted the entire project to go together without fasteners.  Originally, my hope was to avoid metal all together, but I couldn't find a way to work wooden springs into the tight spaces.

The first step was to align all of the maze/body boards together to ensure the marble would move freely, and fall through the holes.  I did this using clamps and various configurations. 

I did not attempt to complete the puzzle.

The main item I wanted to test here was that once the "block" was all together, could I assemble the internal parts from the outside?  Once the key goes in, the whole thing is locked in place, and cannot be disassembled--if you remember from previous steps, there is a dowel that engages with a cut-out inside to keep the key from just coming out.  This is the last part of the assembly, wherein if the main assembly was glued together, there's no taking it apart.  The answer was "yes, it works".

Once I confirmed the fit and operation of all the parts, I brushed on wood glue and clamped the parts together to dry overnight. 

You'll notice in the photos that the assembly is not flush on all sides.  This was a result of aligning all of the internal spaces to fit nicely.  Once the glue dried, I sent this through my table saw to true up the outside edges.

Step 8: Finishing!

After all of the fabrication, I added stain and varnish.

I chose the darker stain because of its richness.  In the end, I only added a single coat of varnish--it was still drying when I gave the gift about 3 days later.

I apologize for not having a final picture of the stained/finished assembly.  I had to wrap this in wax paper in order to pack this for flight... only after the varnish dried did I complete the final-not-ever-to-be-undone assembly.

To this day my brother has not finished the puzzle, nor has he tasted the sweet treasure that lay inside.  My brother tells me that he uses this in his office as "art" (really just a paper weight), but apparently is a great conversation starter!

"What's that block of wood for?"

The object is that you must use a single marble, sound, gravity, and what's left of your sanity, to navigate through two levels of complex mazes before coming to the end--where the marble is now the "key" to unlock the treasure hidden within. 

If anyone wants the CAD model, let me know. 


Step 9: Solid Models for YOU

....sorry for finally getting around to it, but here are the models.

3D Design Contest

Runner Up in the
3D Design Contest



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    19 Discussions

    This looks awesome! I love these kind of puzzles that make the gift recipient work for the goods.


    6 years ago on Introduction

    I agree that this could be a great product! I've never seen anything like this before. It's a great way of giving the others their presents :)


    4 years ago

    Hello great maze i want to make it for a geocache van i have the cad files fort it please!? great job you did thanks in advance!

    1 reply

    5 years ago

    May I please have copy of CAD files?

    1 reply

    6 years ago on Step 8

    I've just started out with woodworking and I'm building a popsicle stick version of this project. Thought it would be a good idea to give this to my future girlfriend (I'm still single).

    Just wondering, do you have to varnish the interior too? Or just the visible parts?

    1 reply

    Reply 6 years ago on Step 8

    finishing was the last thing that i had done, i stained the small parts 100%. but only stained the outside of the maze.

    as for varnish, i was careful to only do the outside, and prevent the varnish from gluing any of the parts together.


    6 years ago on Step 8

    Since no one will be able to look into the maze anyway.


    6 years ago on Introduction

    Great instructable. Have you thought of marketing it? I'd be interested in trying my hand at making it.

    1 reply

    Reply 6 years ago on Introduction

    I had never considered marketing it until now. You're the second person this month who has suggested it.

    When you make yours, be sure to post it!