Just Fit Puzzle Project


With another Christmas looming, it was time to get my head down and think about my annual wooden puzzle project to give to my brother as a Christmas gift. Each year I try to create a puzzle for him which I hope will have him totally stumped, and yet each year he seems to solve them much, much too quickly.

So I started scouring the internet for ideas and existing puzzles which I could try to emulate [cough] copy [cough] myself.

I came across a number which seemed pretty good but in the end I settled on one which I felt had a good mix of visual interest, adequate difficulty and also was relatively simple to make. It was called Just Fit by a guy called William Strijbos and it won the Hikimi Puzzle Competition in 1990, which was a competition for wooden made puzzles.

The puzzle is made up of 16 pairs of blocks which are glued together side by side. Half the squares are black and the other half unpainted. The blocks also feature an angled edge. The aim of the puzzle is to place all of the blocks into the box provided such that they sit flush with the top edge of the box. Also the checkerboard pattern must be maintained at all times. Seemed pretty difficult I thought, I just hoped it would be difficult enough to foil the puzzle-master (aka my brother)

So as always I began by designing the puzzle in 3D on my home computer. By doing this I am able to figure out all of the dimensions and required stock before I ever even enter the workshop. It also helped me to ensure the solution I had was actually correct and that the puzzle would be solvable.

As always, I started by creating the design in 3D on my computer

Once I had the design I headed to the workshop. I decided to make the project out of oak. I think oak is a beautiful looking wood and takes finishes very well. Also I had about a tonne of small off cuts lying around the workshop which would basically be perfect for the job.

I used a couple of spare pieces of oak lumber I had lying around the workshop.

The first step was to cut the lumber into square cross sectional strips. For this I just used the table saw.

I initially cut the lumber down on the table saw…

…into strips of wood which were all uniformly square

Once I had equally sized strips, I set the table saw angle to approximately 10 degrees. The exact angle didn’t matter too much, so long as each block used the same angle in the end.

I set the table saw to an angle of about 10 degrees and cut each strip along one edge

With the stips cut I gave them all a light sanding, being very careful not to make one strip smaller than any other one as this could stop the puzzle from working properly.

I lightly sanded each of the strips down on the belt sander

The next step was to cut the strips into equally sized square blocks. Each block would have one angled face. Before starting this however, I stuck tape to each of the strips’ bottom faces. This is a common technique to help prevent splinters of wood from “tearing out” of the bottom side of a cut.

Before I started to cut the strips, I covered the bottom faces with masking tape to prevent tear-out

Next I set up my mitre saw to cut 90 degrees and also clamped a stop block onto one side to act as a guide for each block that I cut. By doing this I was guaranteed to get equally sized blocks each time.

I used a stop block on the mitre saw to ensure each block was exactly the same size

Here are some of the cut blocks

All of the finished blocks with the tape removed

With the blocks cut I lightly sanded each one with 120 grit sandpaper, again being careful not to adjust the overall size of the blocks too much.

I sanded each of the blocks lightly by hand

At this point I needed to paint half of the blocks black to get the checkerboard pattern. I used a really nice opaque wood stain which I had left over from another job.

In order to get the checkerboard pattern, half of the blocks needed to be painted black

Once the paint was dry I had to glue the blocks together. However this was the most critical part of the project. The orientation of the blocks was essentially what made the puzzle work and so any mistakes here would probably ruin the entire project. So to be sure I had the orientations right and didn’t make any mistakes, I made myself a plan on paper of how to attach the pieces and ticked each one off the list as I went.

Because the orientation of the blocks was critical, I made myself a plan on paper to help me know which way the blocks should be glued

I needed pretty much every clamp in my workshop for the glue-up

The next stage in the project was to make the box for the puzzle. Again I decided to make use of some spare pieces of oak I had left over from another project. However I didn’t have anything which was wide enough for the job and so I had to join some pieces together. I made sure to select pieces which looked similar in grain and pattern.

To create the puzzle box I decided to use some offcuts of oak I had in the workshop.

I selected some pieces which roughly matched in terms of grain and pattern

With the pieces selected I edge jointed the sections together.

I then planed the edges of the pieces flat to ensure a good gluing surface

I added glue to the edges

And then used a few other clamps to hold them together

With the glue dry they were ready for shaping

Because I only wanted thin pieces for the sides and bottom, I cut each section down the middle on the bandsaw, leaving me with several thinner strips. I tidied these up with a plane and sander.

I cut each section into slices on the bandsaw to produce thinner sections

You can see the thickness of the slices

I used a plane to flatten the surfaces

And also a light sanding

All the pieces flattened and sanded

Then I edge jointed three pieces together to form the bottom of the box and clamped it all up.

The bottom of the box was edge jointed and glued

For the sides I used my mitre saw to cut 45 degree mitres on each section, again using a stop block to ensure each edge was the same size. This was then all glued and clamped together.

To create the box sides I had to cut 45degree mitres on each of the sides

The finished edges

I used a few different clamps to hold the edges together during the glue-up

Once both the sides and bottom were glued I glued them together as well.

Once the glue was dry on the bottom I sanded it all smooth

I glued the bottom onto the edges

…and used several clamps to hold it together during the glue-up

One last sanding all over and the box was finished.

Once dry it just needed a final sanding

Here are some pictures of the completed puzzle. Frustratingly when I gave it to my brother on Christmas day, he actually solved it within about 10 minutes!! I had expected him to solve it, but that’s just plain ridiculous. I think next year I will have to be much more inventive if I’m going to catch him out 🙂

Here is the finished puzzle

And another photo

Frustratingly my brother solved it about 10 minutes after he unwrapped it on Christmas day!!