*Pulley A simple machine used to lift heavy loads and save effort.
*The pulley is a small wheel that has a groove around its axis and can rotate about its axis.
*A simple mechanism consisting of a disk that rotates around a central axis and a flexible cable that runs across the disk (rope, tape, wire, chain, etc.) can rotate around the central axis called a pulley.
*It can change direction of pulley, steel rope and can lift high weight cargoes, especially series of pulley combined with windlass, mast and other lifting machinery. They are widely used in installation in construction and divides into hook type(open type) and ring type(closed type).