A top drive is a mechanical device on a drilling rig that provides clockwise torque to the drill string to facilitate the process of drilling a borehole. It is an alternative to rotary table. It is located at the swivel place and allows a vertical movement up and down the derrick. An advantage of a top drive is that it allows the drilling rig to drill longer sections of a stand of drill pipe. A rotary table type rig can only drill 30-foot (9.1 m) (single drill pipe respectively) sections of drill pipe while a top drive can drill 60–90-foot (18–27 m) stands (double-triple respectively. A triple being three joints of drillpipe screwed together.), depending on the drilling rig type.