Nut, in technology, fastening device consisting of a square or hexagonal block, usually of metal, with a hole in the centre having internal, or female, threads that fit on the male threads of an associated bolt or screw. A bolt or screw with a nut is widely used for fastening machine and structural components. nut.
A nut is a type of fastener with a threaded hole. Nuts are almost always used in conjunction with a mating bolt to fasten multiple parts together.