drive nail through hole in jig to match center
use nail as pivot point for cutting circle
Cut a Circle
To use the jig to cut a circle, draw a line on the work piece from its center to the end of the desired radius of the circle. Center the router atop the end point of the radius. Drive a nail through the appropriate hole in the jig that corresponds with the center of the work piece (image 1). Set the router to the proper depth, and make a slow pass through the work piece, using the nail as a pivot point (image 2). Make deep cuts in several passes, lowering the router bit slightly after each pass.