A jigsaw provides a fast, safe way to cut plywood. The catch: It's nearly impossible to keep the narrow blade cutting straight when sawing the thin sheets. The solution is to clamp a pair of straight-edge boards in place to serve as a saw guide. Place the first guide board on the paneling parallel with the cut line. Hold the base plate, or shoe, of the saw against the board to be sure the blade is lined up with the line. Then remove the saw blade, place the tool against the first guide and position the second guide tightly against the opposite edge of the shoe before clamping it down. Repeat this procedure at the other end of the guides to create a perfect-width channel. Then reinstall the blade and slowly push the saw through the channel for a straight cut.