Mechanical device used chiefly on board ships or in shipyards for moving heavy weights by means of ropes, cables, or chains.
A capstan consists of a drum, driven either manually or by steam or electricity, that rotates about a vertical axis to wind in a line wrapped around it. The grip between the line and the drum depends on friction and on the number of times the line is wrapped around the drum. A notched track ( ratchet ) on the base plate and pawls attached to the drum prevent backward rotation.