How to Make Router Lines in Plywood

Place the sheet of plywood on a flat surface or on two saw horses. Measure and mark both edges of the plywood, indicating the positions of the routed grooves. Mark cutting lines between opposite edge marks. If you do not intend to rout a groove all the way across the board, mark where the grooves begin and end.

Loosen the chuck on the router. Install the router bit, then tighten the chuck. Carefully measure and note the distance from the center of the bit to the edge of the base plate of the router. This will be the distance from the marked cutting line to the edge of the jig.

Lay the lumber plank on the plywood so it is parallel to the first cutting line. Measure to ensure that the plank is the same distance from the line as the space between the center of the bit to the edge of the router's base plate. Clamp the plank to both edges of the plywood.

Turn the router on. Hold the router with two hands. Press the base plate firmly against the jig. With the base plate flat against the surface of the plywood, cut the groove from left to right. Push the router toward the end of the line. Do not pull it toward yourself.

Measure, reposition and clamp the jig in place to make additional grooves.