As with all quality marking knives, the blade has the bevel on one side only. This design allows the flat side close contact with your straight edge or square. A cut line is far more accurate than a pencil line. The great benefit, particularly when working across the grain, is the ability to register your saw or chisel in the cut. The 20mm(3/4") wide by 150mm(6") long blade has hardwood scales, through pinned with three brass rivets to form an easily gripped handle. The high carbon steel blade holds a good edge.