A secret compartment shelf can be used to store valuables. when closed it appears to be a simple floating shelf. When opened with a magnet you have access to a hidden compartment. I placed a magnet on the side of the drawer to the small box I made. By simply placing the side of the box under the magnetic lock, the bottom of the shelf is unlocked.
Step 1: Hardware and Material Cut List
Two child safety magnetic cabinet locks $10
Two frameless surface mount spring hinges $10
(optional) One super magnet $4
1 and 1/2 inch thick gray high density polyurethane foam. 6 1/2" by 16 1/2"
One piece 3/4 by 7 1/4 x 22 1/4 (top)
One piece 3/4 by 1 3/4 x 23 3/4 both ends mitered at 45 degrees (front trim)
Two pieces 3/4 by 1 3/4 x 8 one end mitered at 45 degrees (side trim)
Support assembly :
One piece 3/4 by 2 1/8 x 19
Two pieces 3/4 by 2 1/8 x 4 3/4
One piece 3/4 by 5 3/4 x 19 3/4
One piece of crown molding 3/4 by 3 x 23 1/2 both ends mitered at 45 degrees
Two pieces of crown molding 3/4 by 3 x 7 7/8 one end mitered at 45 degrees
Note: all crown molding measurements are made from long point to long point.
Step 2: Top Assembly
(Optional ) the front and side trim pieces can be given a decorative face.
I installed a 1/4" core box router bit on my router and set the fence at 3/8. I ran the piece of wood through the router the rotated giving the piece. to even spaced grooves.
Set the miter saw to 45 degrees and miter both ends of the front trim piece.
Keep the saw at 45 degrees and cut the side trim pieces oversized.
Set the saw back to 90 degrees and cut one end to 90 degrees.
Apply glue to the trim pieces and top. Use clamps to keep everything together while the glue dries.
Step 3: Painting Hardware and Making Analternative Magnetic Key.
While the glue is drying you can sand the locks and hinges with 220 grit.
You can use the magnetic key the lock kit came with or you can make your unique key.
I made a simple bandsaw box and drilled a 5/8" hole on the side of the drawer. I placed some epoxy inside the hole and placed a 5/8" strong magnet inside. I finished everything off by flocking the drawer. This concealed the magnet and will prevent the drawer from scratching the bottom surface of the shelf when opened the shelf.
Step 4: Shelf Support Assembly
Cut all pieces to with and length.
Predrill the long piece by placing two holes 3/8 on an inch in from each end.
Apply glue to the end of the two small pieces and stand up horizontally.
place the long piece over the two small pieces line up flush and drive two 1 5/8 wood screws on each side.
Step 5: Bottom Assembly
Cutting the crown molding:
When cutting the crown molding, ensure the bottom bevel is tight up against the fence of the saw. The top bevel of the crown molding should be sitting flat (ONLY ON THE BEVEL). when you have the crown molding n the saw it should be upside down.
If you have never cut crown molding before I suggest you practice with a cheap piece of crown molding first.
Miter the front piece of crown molding to 45 degrees at both ends.
Miter the two smaller pieces to 45 degrees at one end.
Apply glues to all surfaces to be joined.
Use painters tape to help line all pieces together.
Clamp all pieces together. this s a difficult glue up and a couple of brad nail can helpful. just remember every nail hole has to be filled later so only use a few nails.
Step 6: Preparation for Joining Support Assembly to the Top Assembly.
Placement of support assembly.
Place all pieces together and check for clearance issues. The support assembly should not be touching the bottom. there should be a 1/8 inch gap. Line up support assembly so there is an even spacing from side to side.
Once you are happy with the placement, remove the bottom assembly and mark the placement of the support assembly with a pencil.
Using a doweling jig, drill four holes on the bottom side of the bottom assembly.
Place dowel centers in all four holes. Flip the support assembly over and place it on the underside to the top assembly. Ensure the support assembly lines up with the marks you made previously. Holding the support assembly in position, place a scrap piece of wood on top and tap down with a hammer. Remove the support assembly and the dowel centers should have left dents in the wood. These are your marks for drilling the holes to the underside of the top assembly.
Note: ensure you do not drill completely through the top assembly.
Step 7: Join Top Asembly to Support Assembly
This is the perfect time to sand everything thoroughly. Start with100 grit, then work through the grits to 180 grit.
Apply glue the edge(where holes were drilled) of the support assembly and insert the dowels.
Clamp the two pieces together while the glues dries.
Apply your choice of stain and finish.
Step 8: Attach Hinges.
To attach the hinges, Place a half inch spacer from the side support piece.
Mark the center of the two oval holes on the hinge.
Predrill the two holes only, set the two screws.
Repeat this step for the other side of the hinge and the other hinge.
Check for alignment by opening and closing the shelf. adjust the hinges until you are happy with the alignment.
Mark the position of the hinges with a pencil. Remove only the two screw from the top assembly. place top assembly aside.
On the support assembly (Left hinge) drill a 1/8 inch through hole corresponding to Only the top left hinge hole.
On the support assembly(right hinge) drill a 1/8 inch through hole corresponding to only the top right hinge hole.
These through holes are going be how you mount the shelf t the wall.
Now predrill and set the rest of the screws.
Step 9: Install the Magnetic Locks
I used double sided tape to help with installation of the locks and catches. By using double sided tape and applying it to the back of the catches and locks, I avoided placing numerous holes on the project.
I couldn't find an easy way to install these locks. I placed the double side tape and set the locks on the bottom on the shelf and the catches to the inside of the side support. I closed and opened the shelf several times until It was pretty close to operational. I predrilled and set the screws on the locks and catches. at this point the, locks and catches still allow for minor adjustments.
Step 10: Cutting and Installing the Foam
Cut the foam using a utility knife or a band saw.
Cut one long side to a 45 degree angle. This will ensure a flush fit .
Mark the location of the locks and hinges and cut the sections out.
Place the foam inside the shelf and double check for clearance issues. Minor trim adjustment might be necessary.
Decided what you want to place inside the shelf and trace around it with a marker. The approximate available storage space is :2 1/2 by 6 1/2x 14 inches.
Using a utility knife cut about 2/3 of the way down the foam. Pull the waste foam out.
Using a spray adhesive or a glue designed to work with foam, glue the foam directly to the bottom of the shelf.
Mount the shelf by driving two 2 1/2 inch screws through the THROUGH holes made on the support assembly.
Make sure your are driving the screws into the wall studs or use appropriate wall anchors.
Place your items in the voids and close the shelf.
To open place a strong magnet under the lock, apply upward pressure to the bottom of the shelf. this releases pressure on the lock and it allows the locking mechanism to disengage.
For further information, check out my build video