This document discusses pulley systems and their uses in physiotherapy. It begins with definitions of pulleys and their components like blocks, tackles, ropes, and shells. It then explains different pulley combinations like gun tackles, luff tackles, and double tackles. Mechanical advantage is defined as the number of rope parts supporting the load. Fixed and movable pulleys are described. The document concludes by giving an example of a simple pulley system used to lift weights in physiotherapy, which has a mechanical advantage of 2.