A nylock nut is a hex nut with a nylon insert at the top that grips the bolt threads, preventing loosening from vibration. It’s strong, reusable (limited times), corrosion-resistant, but not suitable for high temperatures.
_1.avif "Nylock nut")
 1.avif "Nylock Nut (Din 985)")
 1.avif "Nylock Nut (Din 982)")