Nut (fastener)

A nut is an accessory fastening component used with some screws and bolts. In general, it has an inner hole that is threaded to receive the male threads of the fastener, and an outer hard shell, usually hexagonal or square, that can be turned with a tool called a wrench. The wrench can be turned either in a direction to tighten or loosen the bond between nut and screw/bolt.