| What it is | A 3:1 hauling system |
| Shape | Rope routed in a Z |
| Main use | Crevasse rescue hauling |
| Difficulty | Advanced |
A Z-pulley, or Z-drag, is a rope hauling system that creates roughly a 3:1 mechanical advantage by routing the rope through anchors and pulleys in a Z shape. It is the standard system for hauling a climber out of a crevasse, letting a small team lift a heavy load with a fraction of the force.
How it works
The rope runs from the load to an anchor and back via a moving pulley, forming a Z that gives about 3:1 advantage (less, with friction). Prusiks capture progress.
When it’s used
The core of crevasse rescue, built off a snow anchor. Educational only; not a substitute for instruction.
Frequently asked questions
What is a Z-pulley?
A Z-pulley (or Z-drag) is a rope-hauling system that gives about a 3:1 mechanical advantage. By running the rope from the load, up to an anchor, back down to a moving pulley on the load strand, and back up, it forms a Z, so each unit of force you pull moves the load with roughly three times the force.
How much mechanical advantage does a Z-pulley give?
Ideally 3:1 — meaning you exert roughly one-third of the load's weight to haul it — though friction in the system reduces the real-world figure. It can be compounded with additional pulleys for more advantage when a load is especially heavy.
When do you use a Z-drag?
Most commonly in crevasse rescue, to haul a fallen climber out of a crevasse, and in swiftwater and general rescue for moving heavy loads. It's a core skill for glacier travel, built from the rope, anchors, pulleys or carabiners, and friction hitches.
Sources
- Mechanical advantage hauling — American Alpine Club
- Crevasse rescue instruction — AMGA