How to Use a Snatch Block (Double-Line Pull)

What a snatch block is

A snatch block is a pulley in a housing with a side plate that swings open, so you can drop a winch line into it without threading the line end through. It does two jobs: it lets you double the line for a heavier pull, and it lets you change the direction of a pull when the anchor is not in line with the vehicle.

It is not a recovery point and it is not a shackle. It is one link in a chain of rated parts: the winch, its line, the block, the shackle and strap that hold the block, and the anchor. The chain is only as strong as its weakest link, which is why this guide starts with ratings before steps.

Three ways to rig a pull

The same winch can be rigged three ways. Pick the one that fits the load and the anchor you have.

Why the line load roughly halves

In a double-line pull the winch line is in two segments between your vehicle and the block. Each segment carries about half of the pull, ignoring friction in the block, so the load on the winch line is about half what a direct pull would put on it. The price is speed: the winch has to spool in twice as much line for every foot the vehicle moves.

The block and the anchor see the combined pull of both segments. That is more than the load on the winch line and can approach twice the line tension, so rate the block, the shackle, the tree saver and the anchor for that, not for the line load alone. Block makers define their ratings in different ways (some describe the line pull, others the total load on the block), so read the maker's definition and your winch maker's manual before you rely on a number.

Real blocks add some friction. Treat "roughly half" as an approximation, not a promise.

Check your gear before you rig

Go through this list before the line comes off the drum:

• The block: a rating from the maker, and a sheave that suits your line type and diameter. Wire rope and synthetic rope are not always interchangeable on one block; the maker's page says which.
• The shackle: a rated shackle with its working load limit marked. See rated shackles vs soft shackles.
• The anchor: a healthy tree with a rated tree saver strap, or another rated anchor. See tree protection straps.
• Your vehicle's points: only the recovery points your maker rates. See recovery point basics.
• A damper on the line where the winch or line maker says to use one. See what a winch damper does.
• The line itself: no kinks, cuts or heat damage. See winch line concepts.

Step by step: a double-line pull

This is the general sequence. Your winch and block makers' instructions come first wherever they differ.

1. Agree the plan.
   One person runs the recovery. Agree hand signals and a stop signal before anything is under tension.
2. Set the anchor.
   Wrap a rated tree saver low on a healthy tree. Never wrap the winch line itself around the tree.
3. Shackle the block to the tree saver.
   Use a rated shackle and close the pin as its maker instructs.
4. Load the line into the block.
   Open the side plate, lay the line in the sheave, close the plate and secure it as the block maker says.
5. Run the line back to your vehicle.
   Hook it to a rated recovery point, not a tow ball or bumper trim. Put the damper on the line.
6. Clear the area.
   Everyone moves well clear of the line, the block and the anchor, including the line's path if something lets go.
7. Spool in slowly.
   Take up slack, check that everything seats, then pull smoothly. Stop at once if a part creaks, shifts or the line twists.
8. Release the tension before you unhook.
   Let the line go slack, then take the rigging apart in reverse order and inspect each part.

Mistakes to avoid

• Hanging the block from a tow hook, tow ball, bumper trim or any point that is not rated for recovery.
• Reading a block's line-pull rating as if it were the total load the block can carry.
• Wrapping the winch line around a tree instead of using a tree saver.
• Dragging the line over sharp rock or a bare edge.
• Using a block whose sheave does not match your line type or diameter.
• Standing near the line or the anchor while the winch is under load.
• Pulling harder when the rig is not working. Stop and reassess instead.

When to skip it, and when to train first

If you cannot confirm a part's rating, cannot find a sound anchor, or have never rigged a double line before, do not try it first on a real recovery. Practise in a controlled place with the vehicle in no danger, and take a hands-on recovery course. For a simpler pull between two vehicles, see how to use a recovery strap.