Pulley and blocks are common lifting mechanisms used for rigging. Using a snatch block in a block and tackle application reduces the amount of force required to lift an abnormally heavy object. A pulley system is used in conjunction with wire rope or other types of rigging ropes, and can be opened on one side to quickly and easily insert a wire rope without having to remove the load or change the direction of the cable, by looping the rope through the pulley (around the sheave) several times before hooking to the object.
The force required diminishes proportionately with the number of pulleys or ''loops'' used during the hoist.
Snatch Blocks are heavy-duty pulleys that act as a pulley point to change the direction of the winch line and are designed primarily for handling heavy loads and can also be used to increase the lifting and pulling capacity of hand-wired hoists and winches. Snatch Blocks allow the direction of the wire to be changed by moving the anchor point so that it can be pulled in a three-point movement. The Snatch Block is ideal for moving loads over short distances and is often used in recovery situations.
Both the Pulley block and Snatch block are pulley blocks with a wheel on the axle. the Pulley block gives direction to the rope when loading and can increase the lifting capacity of the winch by increasing the number of ropes. The difference between them is that the pulley block is continuously closed and the rope must be passed through the shaft, whereas the snatch block is open and has a door on the side so that the wire rope is easy to install.
When used with the winch, both the snatch block and the pulley block can greatly increase the power of the winch, making it run more smoothly and easily.