From Wikipedia, the free encyclopediaJump to navigationJump to searchThis article is about the fastener. For the screw as a mechanism, see Screw (simple machine). For other uses, see Screw (disambiguation).
An assortment of screws
A screw is a type of fastener, in some ways similar to a bolt (see Differentiation between bolt and screw below), typically made of metal, and characterized by a helical ridge, known as a male thread (external thread). Screws are used to fasten materials by digging in and wedging into a material when turned, while the thread cuts grooves in the fastened material that may help pull fastened materials together and prevent pull-out. There are many screws for a variety of materials; those commonly fastened by screws include wood, sheet metal, and plastic.