K nut, also known as K-cap or toothed nut, is a nut with a special structure. A movable tooth piece is pressed into one end of the hexagonal nut by stamping. It is mainly used for locking and preventing loosening, and plays an important role in many fields such as mechanical equipment and construction engineering. The specifications of K-nut range from M6 to M64, and the materials are divided into carbon steel, stainless steel, high-strength steel, etc.