A screw, or fastener, is a sort of latch, ordinarily made of metal, and described by a helical edge, known as a male string (outer string) or simply string, wrapped around a barrel. Some screw strings are intended to mate with a correlative string, known as a female string (inner string), frequently as a nut or an item that has the inside string framed into it. Other screw strings are intended to cut a helical furrow in a milder material as the screw is embedded. The most widely recognized employments of screws are to hold questions together and to position objects.

Screw is a framework that progressions over rotational development to direct development, and a torque (rotational force) to a straight compel. It is one of the six conventional essential machines. The most generally perceived structure involves a tube formed shaft with helical wrinkles or edges called strings around the outside. The sink goes through a hole a substitute thing or medium, with strings inside of the crevice that work with the screw's strings. Exactly when the post of the sink is rotated appreciation to the stationary strings, the screw moves along its center concerning the medium incorporating it; for occasion transforming a wood screw powers it into wood. In screw frameworks, either the screw shaft can turn through a hung hole in a stationary thing, or a hung neck area, for instance, a nut can rotate around a stationary screw shaft. Geometrically, a screw could be seen as a tight inclined plane wrapped around a barrel. Screws are in like manner used as linkages as a piece of machines to trade power, in the worm gear, lead screw, ball screw, and roller screw. In view of their low capability, screw linkages are seldom used to pass on high power, yet are more every now and again used in low power, spasmodic uses, for instance, arranging actuators.