Autoblock

An autoblock (or autobloc or "third hand") is a rope device used in climbing and caving for both rappelling (downward) and ascending (upward).[1][2]

An autoblock using a Prusik knot on the left and an autoblock using the Machard knot ("autoblock knot") on the right.

While rappelling, it slides freely down the rope when pushed downward by the hand, allowing a controlled descent, but jams in the event of a sudden drop or loss of control, stopping the descent. This prevents uncontrolled falls in the event of an accident in which the abseiler loses control of the rope.[3] For ascending, it likewise can be pushed up the rope manually when unweighted, but jams and holds when weighted by the body.

It is made using a friction hitch around the rope, connected by a carabiner to the climber's harness, and may be combined with other climbing equipment for further safety.[4] For instance, it is typically used as a backup while rappelling using a tube belay device.[1]

The term autoblock is also used for a specific type of friction hitch,[5][2][6] which is also known as a French prusik or Machard knot, named after its inventor, Serge Machard.[7][8]

Other friction hitches that can be used to build an autoblock system include the Prusik knot, Klemheist knot, and Bachmann knot.

The Ashley Book of Knots #505.

References
  1. "6-Step Guide to Rappelling with an Autobloc Backup". Devils Lake Climbing Guides. Retrieved 2018-07-10.
  2. Gaines, Bob; Martin, Jason D. (2014-05-20). Rock Climbing: The AMGA Single Pitch Manual. Rowman & Littlefield. ISBN 9781493009626. Sometimes called the “third hand,” the autoblock is ... friction hitches like the prusik, klemheist, and autoblock
  3. "How to Tie and Use an Autoblock Knot for Climbing". Retrieved 2015-04-24.
  4. "6-Step Guide to Rappelling with an Autoblock Backup". Retrieved 2015-04-24.
  5. "Canyoneering 101 - Autoblock | The Dye Clan". dyeclan.com. Retrieved 2018-07-09. The term "autoblock" is kind of ambiguous as it refers to both the knot and the system. As such, you can create an autoblock system with the autoblock knot, a Klemheist (French Prusik), or a valdôtain tresse.
  6. Rock climbing. Kidd, Timothy W., Hazelrigs, Jennifer., Wilderness Education Association (U.S.). Champaign, IL: Human Kinetics. 2009. ISBN 9780736068024. OCLC 251227945. Examples of appropriate hitches include autoblock, klemheist, and PrusikCS1 maint: others (link)
  7. "The Machard Knot". Retrieved 2016-10-20. the Knot invented in 1961 by Serge Marchard, a young climber from Marseille
  8. Vola, Eric (2016-06-03). "Le noeud Machard et son histoire - CAF Marseille Provence" (in French). Archived from the original on 2016-06-03. Retrieved 2018-07-09. [from French] Serge had sent André a letter on December 28, 1961 which among other things included the description of his knot. The two diagrams of his letter are reproduced here.


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