Most carpenters scribe with a compass or a small block of wood. That works fine but requires a practiced hand to keep the pencil line parallel to the scribed surface. The M.Power Perfect Butt Profile Scriber makes the task easier. It's basically a pencil sheath with a freely moving wheel at the drawing end. Because the pencil point is at the center of the wheel, the drawn line will always be perfectly parallel to the scribed surface. The tool comes with four different sizes of wheels and can scribe distances ranging from 1-1/16 inch to 3-1/2 inches.