Rigging Basics: The Snatch Block

A typical rigging set up includes any number of components including blocks, hooks, chains, ropes, and slings. The snatch block is but one of those parts. Snatch blocks are usually manufactured with either shackles or hooks for connecting them with other parts of the rigging set up.

This post will discuss the basics of the snatch block. You will learn what snatch blocks are used for, how to use them safely, and so forth. We hope you will take a few minutes after reading this post to check out our entire inventory of rigging supplies.

Snatch Blocks and Winches

A snatch block is a very simple piece of equipment. Generally used with either a winch or boom, the snatch block is essentially a pulley with an accessible side plate that alleviates the need to thread rope or cable through the pulley. You may think this is not a big deal until you are presented with a piece of cable with a loop on the end; a loop you cannot thread through the pulley.

There are two purposes for including snatch blocks in a rigging set up. The first is to increase pulling power by distributing the weight of a load over more area. The second is to change the direction of the pull if necessary. A direction change can be accomplished by offsetting the anchor point of the snatch block in question.

Increasing Pulling Power

The first use of the snatch block is something you have probably observed more than once in your lifetime. Snatch blocks are added to a rigging set up in order to increase pulling power. The more blocks in the setup, the less power required to lift the load. However, the downside is that more blocks require more rope or chain.

The science behind this principle is actually quite simple. Introducing a block evenly distributes the force of the load being lifted. Rather than lifting dead weight, you are applying just enough force to carry the load along the pulley of the block. The block takes the remainder of the load on the other side. Adding additional blocks further reduces the needed lifting power by further distributing the load.

Changing Load Direction

A less common use of the snatch block is to change the direction of a pull. Let’s say you are a toll operator trying to recover a vehicle on the side of a busy highway. You might use a single block along with two chains to pull the vehicle up. But what if you also wanted to pull it out?

You could use a second snatch block with an offset position to accomplish just that. By carefully placing your snatch blocks in the right position, you can lift the car both up and out at the same time.

Using Blocks Matches Safely

As with all things rigging, safety is a top priority with snatch blocks. The first thing is knowing where to place them within the rigging set up to ensure maximum efficiency with the least amount of risk. Suffice it to say that it does matter where blocks are placed.

Second is knowing the working load limits of each block in your configuration. Blocks have to be capable of sustaining the load being placed on them, so it’s not good enough to merely guess.

Finally safety requires understanding the direction a load will be pulled in based on block configuration. It is a lot like understanding the direction a tree will fall as you cut it. Safely using snatch blocks means planning ahead of time so that your load moves in its intended direction.