Single Rope Technique

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Single Rope Technique (SRT) is a method (or rather set of methods) used in caving and potholing to descend and ascend vertical drops ("pitches"). SRT is also used in roped access for building maintenance.

Modern SRT uses specialised devices for both descent and ascent, and low-stretch kernmantel rope of 8 mm-11 mm diameter.

Descent (abseiling or rappeling) uses various forms of friction brake to control speed. The most commonly used are the Petzl "stop" (self-locking) and "bobbin", and four or five bar "racks". For safe SRT, especially on drops with complex rigging with intermediate belays, it is essential that the abseiling device can be removed from the rope without being unclipped from the user's harness.

For ascent ("prussiking"), cammed devices ("ascenders") are used that can be pushed up the rope but that lock and hold the user's weight when a downward force is applied; these must also be easily removable from the rope without being detached from the user. (Prusik knots are used to ascend ropes in emergencies in climbing and mountaineering.)

Various prusik systems have been devised. They can broadly be divided into:

"Sit-stand" systems, in which one ascender is at chest level and attached to the user's sit-harness, and another carries a long loop for the feet. Movement up the rope is by repeated moving of the foot-loop ascender up the rope, pushing up with both feet together, and sitting on the chest ascender.
"Rope-walking" systems, with one ascender attached directly to one foot, and another, roughly at chest level, attached to the other foot by a rope; some systems also include a chest ascender attached to the harness. Movement up the rope is by alternate stepping movements with the feet.

Other essential items of a personal SRT set are a sit harness and one or more safety cords ("cows-tails") terminated in karabiners, for temporary attachment to safety ropes at the heads of drops and used in manoeuvres at intermediate rope belays.

Most cavers favour the sit-stand method, and make extensive use of complex rope rigging with intermediate belays and "deviations", so that the rope nowhere rubs against the rock, and to avoid hazards such as loose rocks and waterfalls.

Many cavers in the southeastern USA favour rope-walking systems, and have traditionally used simple rope rigging, with the rope belayed only at the top of the drop (the "indestructible rope technique").

References

Alpine Caving Techniques, G. Marbach & B. Tourte, Caving Publications International 2002, ISBN 3-908495-10-5.
Single Rope Techniques, D. Elliot, Cordée 1987, ISBN 0904405680.
On Rope, A. Padgett, National Speleological Society (USA), ISBN 1879961059.

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