An interior door was purchased to replace a broken door (not shown) but the new door was 1" too tall. Accordingly, the bottom had to be trimmed. The circular saw has a laser guide, which makes a red line (barely visible on the black tape). In addition, a 2x4 wood guide was clamped so that the circular saw would make a straight cut. The black tape was used to prevent the saw blade from ripping out chunks of the exterior door (the tape was removed after sawing). In the photo, the door is about to be cut.