High Quality Content by WIKIPEDIA articles! A derrick is a lifting device composed of one tower, or guyed mast such as a pole which is hinged freely at the bottom. It is controlled by lines (usually four of them) powered by some means such as man-hauling or motors, so that the pole can move in all four directions. A line runs up it and over its top with a hook on the end, like with a crane. It is commonly used in docks and onboard ships. Some large derricks are mounted on dedicated vessels, and are often known as "floating derricks".