Quickly and accurately mark centerlines on boards up to 2-1/2" thick. CenterFinder straddles your board to mark a perfectly centered line along the face or edge of boards. Insert the pencil into the center hole, rotate the tool so the guide posts contact the material, then scribe. For marking offsets use the CenterFinder on one the flat sides and select your offset. Use the pencil in the offset notches to mark or draw your line. Milescraft 8408 CenterFinder