How to Cut Plywood Straight

Place the plywood face down on a pair of sawhorses. Cutting it from the back will minimize chipping from the saw blade on the edge of the visible face.

Measure the width of the cut from one edge with a tape measure. Make pencil marks on either end of the plywood and one in the middle. Align a straight edge on the marks and draw a line along the edge with a pencil.

Loosen the saw blade depth adjustment lever on a circular saw and set the depth of the blade to slightly more than the thickness of the plywood. Tighten the lever and attach the guide that came with the saw if the width is within the limits the guide can accommodate.

Place the saw at the beginning of the pencil line and adjust the guide so it fits tightly against the edge of the plywood when the blade is touching the side of the line opposite the edge. Start the saw and begin cutting, keeping the base of the saw flat against the plywood and the guide tight against the edge as you progress. Cut all the way past the opposite end of the plywood and let the piece you have cut fall away.

Construct a temporary guide if the width of the piece you want to cut is too wide for the guide that fits on the saw. Measure the distance from the edge of the blade to the outside of the saw base and make marks on the plywood the same distance from the line. Place a straight board on the marks and clamp it to the plywood with C-clamps.

Reset the depth of the saw blade to slightly more than the thickness of the plywood and set the saw at the beginning of the line. Turn it on and begin cutting, keeping the edge of the base in contact with the guide as you cut. Cut past the other end of the plywood and let the pieces separate.