A geometry board is a simple peg board that can be used by kids (and adults) to experiment with shapes by simply stretching rubber bands around a grid of nails. My daughter asked me to make one for her and the entire job took about 30 minutes from start to finish.

Step 1: Measuring and Cutting the Board

Here's what you'll need to make a geometry board:

a piece of wood (find a piece of scrap in your garage or check the scrap bin at the lumber yard).
some kind of saw. I used a table saw and sliding compound saw but a circular saw or hand saw will work fine.
carpenter square
drill for pre-drilling holes for the nails.
sand paper.
wax for finishing.

My daughter set the size for this board which is 7" x 7" x 3/4" with 36 nails spaced one inch apart. Start by measuring with a tape measure and making a pencil mark at 7" from the edge. If you have a table saw, rip the board lengthwise.

Step 2: Squaring Off the Board

After your initial cut, dimension the board across the grain and make your second cut. Now you should have a square piece of wood.

Step 3: Layout the Grid

Using a carpenter square, mark the board at 1" increments. Use your square to draw lines the length of the board. Do the same thing across the grain and you will have a grid that indicates where you will drill your holes.

Step 4: Drill Holes

Determine what diameter nails you'll be using and select a drill bit smaller than your nails (I used 8 p finish nails but you can use just about anything you have at home). If you have a drill press, set your depth gauge so your drill bit doesn't quite go through the bottom of your board. If you're using a hand drill like I did, use a piece of masking tape to indicate your desired depth and drill to that mark. Drilling vertically is important so use the bubble level on top of your drill (if you have one) to make sure your holes are plumb. If they're a little off, don't sweat it.

Step 5: Sand and Wax the Board

Now is a good time to sand and wax the board. Once the nails are in place, you won't have easy access to the top surface. Sand the top, sides and edges of the board with a medium grain sand paper (I used #120). Get all the sawdust off and apply a light coat of paste wax. After the wax has dried for a couple of minutes, rub off the excess and repeat the step. Now your ready to start nailing.

Step 6: Adding Nails

Start tapping in your nails. Don't worry if they are not the same depth to begin as you'll even them out after they're all in place. Take care not to penetrate the bottom of your board. Once the entire grid is in place, tap to nails down and make them even-ish.