A nut is a mechanical fastener with a threaded hole. It is attached to a bolt, screw or stud to provide a clamping force and prevent axial movement. The shaft of the bolt prevents radial movement of the parts, while the head of the bolt and the nut together prevent axial movement.

Washer, machine component that is used in conjunction with a screw fastener such as a bolt and nut and that usually serves either to keep the screw from loosening or to distribute the load from the nut or bolt head over a larger area. For load distribution, thin flat rings of soft steel are usual.

A bolt is a mechanical fastener with a threaded shaft. Bolts are closely related to screws, which are also mechanical fasteners with threaded shafts. These types of fasteners are typically inserted through two parts, with aligned holes.