Step 1: Tools and materials
- A plastic protractor
- A piece of wood
- Some screws
- A piece of wire or a long finish nail and a hex nut
- Magnetic cabinet door catches (optional)
- A table or radial arm saw
- A rule (and a square)
- An electric drill or drill press and bits
- A countersink bit
- A file
- A pair of pliers to bend wire, or a welder to weld a hex nut to a finish nail
- A level
- A grinder
The photo shows a commercially available angle finder. It reads 360 degrees. A protractor has readings for 180 degrees, but that will be no problem for a reason explained later. While the commercial version is not expensive, it is more fun to make your own.
(The photo is from Lowes.com.)
Step 2: Cut a piece of wood
Saw your piece off to be a little longer than the base of the protractor, and so the corners are exactly square. Check with a good square and by measuring the diagonals. These things really need to be very accurately done, or the whole tool will be compromised.
The square is a larger tri-square I have long wanted. See this Instructable for how I made it.