A nut is a type of fastener with a threaded hole. Nuts are usually used opposite of a bolt to fasten parts together. The nut and bolt are held together by their threads' friction, a slight stretch of the bolt, and compression of the parts. In instances where rotation or vibration work a nut loose, different locking mechanisms may be used like adhesives, lockwire, and washers. Nuts are widely used in machine assembly and for assembling parts in industrial, construction, and military applications.