Learning how to use a snatch block is an essential vehicle recovery skill for off-roading and overlanding. A snatch block is a heavy-duty pulley inside a metal casing that is typically used with a winch to recover a stuck vehicle.
Snatch blocks can serve two purposes in off-road vehicle recovery: 1) increasing the pulling force of a winch and 2) redirecting the force of the winch cable to pull the stuck vehicle from a variety of angles. This versatility extends the capabilities of your winch, allowing for recovery of heavier or seriously stuck vehicles or rescues in challenging circumstances.
This article is intended for informational purposes only and is not a replacement for formal, hands-on training. Off-road recovery of vehicles can be dangerous. Check out your local off-roading club or other training programs for basic instruction on off-road recovery techniques.
How to Use a Snatch Block
Snatch Blocks can be used in a number of different scenarios and configurations in off-road recovery. Here, we’ll cover several common techniques. The physics of using snatch blocks can be a bit counterintuitive, but we’ll try to explain where it’s easy to make errors in these common scenarios.
Modern snatch blocks used for vehicle recovery in overlanding and off-roading are fairly simple devices, comprising a pulley (also known as a sheave) sandwiched between two metal side plates and held together with a pin. The side plates can be twisted apart to wrap the winch line around the pulley. When the side plates are lined up, the two holes form an eye that is used to attach the snatch block to an anchor or vehicle using shackles and (in some cases) tree savers or other recovery straps.
Using a Snatch Block to Increase Winch Pulling Force
A snatch block bolsters the pulling force of the winch by providing mechanical advantage, a function of passing the winch cable around the snatch block’s pulley and back to the vehicle. In the case below (Technique #1), the snatch block is used to roughly double the pulling force exerted by the winch in a self-recovery situation where a tree is used as an anchor. It’s not quite double the force, because of friction added by the snatch block itself.
The winch cable extends from the winch on the vehicle through the snatch block and back to a secure recovery point on the vehicle. While the snatch block reduces the pulling force required by the winch, note that the anchor (the tree in this case) is still bearing the entire load of the vehicle. This is one of the most common recovery techniques with a winch and snatch block. You could anchor directly to the tree-saver with a shackle instead of a snatch block, but using the snatch block has the advantage of reducing the strain on your winch.
Here’s a tricky nuance to the physics. If the end of the winch cable attached back to a tree instead of the vehicle, as pictured below, the tree won’t move and so the cable won’t move through the snatch block. Since the line is static between the trees, the winch would be required to pull the full load of the vehicle. This is basically the same as attaching directly to the tree-saver with no snatch block involved.
Another common technique involves two vehicles, depicted below, where one vehicle is stuck and the other uses its winch to rescue it. The snatch block is connected to the stuck vehicle with a shackle at a sturdy recovery point. The winch cable runs from the recovery vehicle through the shackle on the stuck vehicle, then connects back to the recovery vehicle with a shackle at a recovery point.
Multiple snatch blocks can be to further increase the pulling power of the winch. Such is the case below, where a second snatch block is attached to the rescue vehicle and the cable passes through it and back to the stuck vehicle. This roughly triples the pulling power of the winch.
This technique can be helpful when the stuck vehicle’s weight exceeds the capacity of the winch or extra force is needed to pull a very stuck vehicle loose.
Using a Snatch Block to Redirect the Winch Cable
Sometimes it is difficult or impossible to use a rescue vehicle winch to pull directly on a stuck vehicle. In such cases, a snatch block can redirect the force coming from the rescue vehicle to pull the stuck vehicle in the ideal direction.
In the situation depicted above, a tree is used as an anchor so that the rescue vehicle can exert pulling force on the stuck vehicle at a 90-degree angle. The snatch block is attached to a tree saver strap with a shackle to prevent damage to the tree. In place of the tree, another large object, could be used, such as a secure boulder. In this case, the snatch block doesn’t reduce the force required by the winch to pull the stuck vehicle – there is no mechanical advantage.
How to Choose a Snatch Block
Several factors should be considered when selecting a snatch block:
Winch Line Pull Rating
A good rule of thumb is to get a snatch block that is rated for roughly twice the weight your winch can pull. If your winch has a 9,500-pound pull rating, for example, your snatch block should be rated to at least around 19000 pounds (9.5 tons). This is because with one snatch block you can pull roughly twice the load that your winch is rated, thanks to the mechanical advantage the snatch block provides (see Technique #1 and #2 in graphics above).
You’ll see snatch blocks suggested for use with certain winches that aren’t quite rated to twice the winch’s line pull rating. The logic behind this is that it’s unlikely when overlanding or off-roading that you’ll actually need to pull twice your winch’s rated pulling force (assuming you’ve chosen a reasonably strong winch, which is another discussion). Still, we recommend erring on the side of getting a larger capacity snatch block to give yourself peach of mind and flexibility.
Winch Cable Diameter
The diameter of the pulley (sheave) in the snatch block should be at least 8 to 10 times the diameter of your winch cable or even larger. For a metal cable, if possible, find a snatch block with a sheave diameter that’s at least 20 times the cable diameter.
It’s worth erring on the side of getting a large snatch block, as they will be more versatile for the various situations you might encounter.
Winch Line Material
Synthetic rope winch lines are generally thicker than metal cables. Some of the newer snatch blocks have larger groves in the pulley to accommodate this evolution and avoiding squeezing the line as it passes around the sheave. Avoid snatch blocks with V-shaped grooves in the sheave, as these can pinch the line. Also, it’s particularly important to look for and remove any burrs or other imperfections in the sheave that might snag the synthetic line.