Sweeney Todd Slotted blades,Are rectangular in shape and have a slotted cut out for blade placement,they have rounded edges so as to avoid digging into the sub-floor creating less resistance on the cut and is a preferred trimming blade by many carpet installers,comes in a box of a 100 and are protected by oiled paper to stop blades rusting,these blades can be used in conjunction with the Crain 726 Pivoting Knife or the Crain Hook handle Knife.