The Martelli rulers have the Martelli no slip material on the bottom of them to hold your fabric in place so you do not have to re-cut and waste material. The material will move with your ruler allowing you to now move your fabric and not your body when making cuts. The rulers are made out of durable plastic so there are no worries about chipping or cutting into your rulers. All of the Martelli cutters are cut on a CNC machine to ensure that they are 100% accurate.