Auto Block
Also known as:French Prusik, Machard Knot
Description
A friction hitch used as an auto-locking backup for rappelling. Similar to a Prusik but uses a single wrap with the tail tucked through the loop. Grips firmly when loaded but slides when manually controlled.
Common Uses
Rappel backup (auto-block belay), ascending rope, progress capture in rescue systems.
When to Choose This Knot
Choose this knot only in the context of proper climbing instruction, inspected equipment, and a complete safety system. Climbing knots are not isolated tricks; they interact with harnesses, carabiners, anchors, belay devices, and partner checks.
Safety Notes
- Use professional instruction and follow the standards of your climbing gym, guide, rescue team, or local authority.
- Perform a partner check before every load-bearing use.
- Retire damaged rope and never experiment with unverified knots at height.
How to Tie
- 1Take a cord loop and place it around the rappel rope below the belay device.
- 2Wrap the cord around the rope 3-4 times, working downward with wraps parallel and flat.
- 3Pass the bottom of the cord loop through the wraps (like the Klemheist).
- 4Connect the loop to your leg loop with a carabiner. It should slide when pushed and grip when weighted.
Common Mistakes
- Practicing the knot correctly once and then skipping inspection under real conditions.
- Using the wrong carabiner orientation or anchor geometry.
- Replacing supervised training with a web article.