Increase friction—Use to increase the friction between threads or the end face of screws and nuts, or increase the friction of both at the same time to achieve the purpose of preventing loosening. Non-detachable nuts are fixed by welding, bonding or punch riveting, but they have certain high reliability requirements when used, and some important occasions require high reliability in preventing loosening and not requiring disassembly. Mechanical fixing - Use mechanical fixings to fix and tighten the threaded parts and the connected parts or between the threaded parts and the threaded parts to prevent loosening.