Cut perfectly fitted tongue-and-groove joints on stock between 1/2" and 3/4" thick with a table-mounted router and this assembly. The tool consists of an arbor with an integral shank, two identical, removable slotting cutters, and a pair of bearings. To cut tongues, sandwich one bearing between the two cutters (as in drawing A). To cut slots, mount one cutter between the two bearings (as in drawing B). Can be used on 1/2" through 3/4" thick material.