Nuts are fasteners with threaded holes that secure to bolts, screws or studs and hold parts together. Once securely fastened, a nut prevents axial movement in connected materials.

The bolt consists of a head and a cylindrical body with screw threads along a portion of its length. The nut is the female member of the pair, having internal threads to match those of the bolt. Washers are often used to prevent loosening and crushing. See also nut; washer.

A fastener (US English) or fastening (UK English) is a hardware device that mechanically joins or affixes two or more objects together. In general, fasteners are used to create non-permanent joints; that is, joints that can be removed or dismantled without damaging the joining components.