The bow is used to impart reciprocating motion to work in the turns, to the spindle mandril of a lathe, to a drill or drill stock, or to an arbor, by coiling the line of the bow once around a pulley or ferrule. As the bow is moved to and from the work rotates in alternate directions. Bows are made of thin strips of whalebone or cane, drill bows usually being of flexible steel with a tensioning device at one end. Various sizes of bow are available and, according to the size and nature of the work, gut, horsehair or human hair is used for the line.