A snatch block is a simple

A snatch block is a simple, but handy piece of equipment that greatly improves the functionality of your winches for trucks. If you have a winch or plan on getting one, putting a sturdy snatch block in your gearbox is a no-brainer. Not only will it increase your winch’s pulling power, but it will also give you more options in self-recovery situations.
Snatch block basics
The snatch block is a pulley block with a side plate that swings open. Because the side plate opens up, you don’t have to thread your winch cable through the opening; instead, you open the side plate, fit the cable over the pulley, and then close the side plate.
A snatch block has two primary functions in recovery winching. One is to change the direction of your winch cable when the anchor point is offset. The second is to increase the pulling power of your winch.