I wanted a way to mark out circles on plywood, cardboard, and other materials but was not happy with standard compasses that are so limited in size. This compass will allow you to draw circles anywhere from 1.5" diameter to 28" diameter. There is a small spacer that is optional to help keep your pencil vertical. The two halves are tightened together with 1/4" bolts and 1/4" wing nuts that I found. You can use two sets to help keep everything straight or just one to utilized the full size capabilities of the setup. The hole that mounts the center to your work piece is also designed to work with a 1/4" bolt. A standard #2 pencil should work fine.

Enjoy!