Screwdriver

A screwdriver is a hand-tool for turning (driving) screws (and sometimes bolts or other machine elements with a mating drive system). A typical screwdriver comprises: an approximately cylindrical handle of a size and shape to be held by a human hand; an axial shaft embedded in, and protruding from, the handle; and a tip found at the end of the shaft, opposite the handle. The handle and shaft allow the screwdriver to be positioned and supported and, by rotating the handle, torque is applied to the tip via the screwdriver's shaft. A screwdriver is typically identified by its tip, which is shaped to fit, or mate with, a screw the head of which has a particular contour, or surface shape. A screwdriver is, thus, a mechanism to apply torque to a screw. Proper use of a screwdriver requires that the screwdriver's tip engages with the head of a screw having the same size and type designation as the screwdriver itself. Screwdriver tips are available in a large variety of shapes and sizes.