Capstans are mechanical pulleys with a vertical axle. On classic sail ships, they’re used to apply tension to ropes in order to hoist and hold sails in place. Early timber capstans had a basic ratchet with which to hold the force applied by the sailors, who levered the rope around the capstan by inserting metal bars through the top and hauling it around in a clockwise direction.
Come the Industrial Revolution (circa 1750-1850) the greater forces at play meant capstans made completely of iron were forged with gears in the head, which were designed to lift anchors and other heavy objects when turned anticlockwise.
Capstans still exist today, but they’re usually driven by a motor or hydraulics – especially in larger vessels where the elbow grease of several sailors can be replaced several times over at minimal cost. A winch is a form of nautical capstan that is used on smaller sailing boats and this is still generally powered by hand.