Whenever I finish a building’s exterior with vertical tongue-and-groove, shiplap or rough board siding, I use the method shown here to make straight, neat cuts. Every 3 ft. or 4 ft., I leave a board long by 4 in. to 6 in. Then I snap a chalkline about 1-3/4 in. down from my intended line of cut. This dimension is. the width of my saw’s baseplate from its edge to the blade. A piece of strapping tacked below this chalkline gives me a ready-made saw guide that will produce a crisp, straight line on the board ends.
Bruce MacDougall, Bridgewater, NH