- 1). Drill holes at approximately 3/4-inch intervals through the center of the stick lengthwise. Use a drill press and a 3/16-inch bit. The holes don't have to be perfect.
- 2). Place a pencil in one of the holes near the end of the stick. Place a nail in an opposite hole on the other end of the stick. Lay the stick down on a 1/4-by-48-by-96-inch piece of fir plywood. Tap the nail with a hammer to stick it in the plywood.
- 3). Grasp the pencil and sweep the end of the stick in an arch pattern, using the nail as an axle to revolve the stick as the pencil draws an arch on the plywood.
- 4). Measure the arch and compare it to its intended location. If the arch is too small, move the pencil to a hole farther from the nail. If the arch is too big, move the pencil closer to the nail.
- 5). Draw consecutive arches, moving the pencil each time until your arch is configured to fit where you need it to fit. Cut the arch out of the plywood with a jigsaw.
Source...