This is an easy puzzle to build and it makes a great gift. It is moderately difficult to solve but, once you know how, anyone can do it.

Step 1: Materials and Tools

You will need

Materials

20 inches of any type of wood 1" x 1" (I chose to use maple)
3/8" dowel 10" long
4 glass or metal spheres 1/2" in diameter. (I bought slingshot ammo)
wood glue
clear finish

Tools:

Saw
Drill press
Drill press vise or clamp
5/8" Forstner bit
7/16" twist drill
Clamps
Combination square

Step 2: Cutting

First thing to do is to cut your 1" x 1" material to length. I chose to use a table saw but you could use a chop saw or hand saw as long as you end up with accurate pieces with squared up ends.

You will need 2 @ 5 1/2" and 4 @ 2 1/4"

Step 3: Layout

Next you will need to lay out where you need to drill. You will need to drill a hole centered 1/2" away from both ends of the 5 1/2" pieces and on one end of the 2 1/4" pieces. I used a combination square to mark X's on the ends of all of my pieces. This ended up being redundant because of the way I used my vise as a jig but it was still a good way of double checking that my vise/jig was accurate and still aligned correctly.

Step 4: Drilling

When I went to drill my holes, it made sense to use my vise as a jig to ensure accurately located holes. I started by putting a 1" Forstner bit into the drill press and clamping it in my vise so that it made contact at 3 points. This would make sure that all of my holes were drilled exactly 1/2" from the end and each side. I then used a C clamp to hold the vise in place, removed the 1" bit and exchanged it for the 5/8" bit.

The 5 1/2" long pieces I drilled 1/2" deep on each end.

Make sure that you remove any chips that fall into the clamping area because that will cause misaligned holes.

The 2 1/4" pieces I drilled 3/4" deep on one end.

I then removed the 5/8" bit and replaced it with the 7/16" twist drill. I stood the pieces on end and drilled through the piece until the bit appeared at the bottom, like in the picture.

Step 5: Drilling the Center Hole

The next step is to drill a hole exactly in the center of the two 5 1/2" pieces. Carefully lay out with a pencil and ruler and drill a hole with the 7/16" drill. You will want to chamfer the holes slightly as shown in the pictures to ensure the dowels slide easily.

Step 6: Cut and Chamfer Dowels

Insert the 3/8" dowel into one of the puzzle pieces and mark the length as shown in the picture. Then chamfer both ends of all the dowels. This will ensure that if there is a slight misalignment the dowels will still move freely back and forth.

Step 7: Assemble and Glue

The next step is very important and care must be taken so that your puzzle will work properly. Don't forget to put the 1/2" spheres into the holes as well as the dowels. Also you need to take care not to use too much glue. I apply a spot of glue as shown in the pictures and then spread it evenly with my finger. If you apply too much, wipe off excess onto a rag. I let the glue sit open for a while to let some of the glue absorb into the wood.

Now is a good time to get some clamps and scrap piece of 1" x 1" material that is less than 2" long. Clamp the puzzle as shown in the picture with the scrap wood as a spacer. Make sure that the spacer is pinched tightly in the center and if the ends aren't flush that the overhang is equal on both ends.

Step 8: Sand and Finish

To finish up your puzzle, remove any excess squeeze out with a chisel or scraper. Then, sand all of the surfaces smooth and flat. You will also want to slightly round all of the corners and edges. This give the puzzle a nice feel and makes you want to hold it in your hands. I finish it off with 3 to 4 coats of spray lacquer sanding with 220 grit sand paper after the first coat..