Pulley blocks and tackle blocks are used to raise and move heavy loads and these devices have been in use since ancient times. The unit consists of a single or a set of pulleys through which a wire rope, chain or cable is passed. One of the ropes is connected to the load and the other end is pulled manually or by electric motors. Pulley blocks and tackle blocks are used in garages, workshops, boats and in stockyards where heavy loads are to be moved. The most common examples are pulleys used to draw water from wells, cranes and hoists, flagpoles and other items.

Pulley blocks and tackle blocks are classified as per the number of pulleys. The more the number of pulleys, greater is the mechanical advantage that is obtained. Also, less effort is required. Pulleys are made from light weight iron or steel castings and have a mounting bore. They are mounted on a shaft along with bearings for smoother movement.

Pulley blocks and tackle blocks are selected as per the safe load that can be lifted (the number of pulleys that can be used to provide the required mechanical advantage). Too many pulleys can cause fouling of the wire rope.