Circular Saw Crosscutting Guide - The Family Handyman Circular Saw Crosscutting Guide. Get perfect 90-degree cuts with a circular saw with this jig. Glue and screw two 3/4-in. plywood pieces together and rip them to 12-in. wide (or larger). Screw the base sides to the base. Rout rabbets on each runner. Finally, screw one runner to the base sides at exactly 90 degrees and then align the other runner parallel and just far enough apart for the saw’s base plate.