We are all familiar with self-centering jigs for routers that have two pins inline with the bit but spaced apart enough to keep the bit on center when the router is twisted. I have 6 dados 30" long and 1" deep that I want to cut. I did not want to drill out space for a nut on my 1/4" bolt/pins. Rooting through my box of junk I discovered a couple of screen door roller with a 1/4" bearing that should fit on the intended pin. Works like charm, little friction