This 3 Notch deep hook blade provides carpet installers and roofing professionals professionals with the perfect balance of sharpness and durability. When carpet and flooring installers are cutting flooring materials, like carpet, film, underlayment, pad and even cove base, toughness counts.And when used for cutting and scoring heavy architectural shingles, it's the same game. These Made in USA Blue Deep Hook Blades fit all fixed blade, retractable and folding utility knives.