A fixture for a router for permitting one end of a finishing tool extending therethrough to be moveable along a radius edge of a countertop for trimming such edge off of the countertop. The fixture includes a base member adapted to be attached to the front surface of a router housing and includes a central front flange rigidly connected to the base member and extending from the base member out toward one end of the finishing tool. Because of the configuration of the fixture, there will be a clearance between the outer edge of the front surface of the router housing and the countertop when the rounded front edge of the central flange is moved along the radius of the countertop while a cylindrical guide surface on the front end of the finishing tool is on the top of the countertop and the cutting edge of the finishing tool trims off a portion of the top front edge of the countertop.