How to Cut a Straight Line on Plywood

Measure and mark the position of the straight line on your plywood along both edges. Measure from the inside edge of the circular saw baseplate to the face of the blade, typically 1 1/2 inches. Make a second mark along each edge, this distance outside the first set of marks.

Select a straight piece of lumber to use as a straight edge. Lay your straight edge onto the plywood. Position the lumber with the inside edge of the lumber aligned with the second set of marks. Clamp this board in position with one C clamp on each side. Open the clamps and set them with the top of the C under the plywood and the screw stop on top. Tighten the screw to lock the clamp in place on each side.

Position the saw, so that the inside edge of the saw base plate is against the edge of the lumber straight edge with the blade aligned on the outside of the first set of marks. Start the saw and cut through your plywood, with the saw riding firmly against the edge of your lumber straight edge. Support the piece you are cutting off securely, so that the material stays level to prevent the blade from binding. Continue cutting to the other side to complete your straight edge.