Anautoblock (orautoblocor"third hand") is a rope device used in climbing and caving for both rappelling (downward) and ascending (upward).[1][2]
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 prusikorMachard 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.
Sometimes called the "third hand," the autoblock is ... friction hitches like the prusik, klemheist, and autoblock
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.
Examples of appropriate hitches include autoblock, klemheist, and Prusik
{{cite book}}: CS1 maint: others (link)
the Knot invented in 1961 by Serge Marchard, a young climber from Marseille
[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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