This is a jig for surfacing with a router. I created it to "square up" a stump to use as a workbench. Mount a router in the middle of a board which is more than twice as long as the diameter of your project. Level supports on each side. Set the router over the highest spot. Lower the bit a 1/16" or so and rout away. Repeat until you have reached the lowest spot. We have basically created a jig that makes the router work like a milling machine (except the cutter moves over the work instead of the work moving under the cutter.) Use the biggest cutter you have (I used a 3/4") and make sure it is a sharp one- preferably carbide.