Vertical caving terminology and methods > Rope access and arboriculture
Often confused with a dual rope system. Where one end of a rope is tied to a person, looped over a high anchor or natural such as a tree branch, creating a doubled rope, then the other end is pulled on by the same person in order to ascend, or paid out in order to descend. Ascending can be done by manually climbing the rope with hands or feet, or by prusiking, or a somewhat clumsy combination of both which is frequently used by arborists. For safety and to allow resting, the person is connected to the end of the rope that they are pulling via an ascender or prusik loop. When pulling on the rope, the rope moves over whatever it is looped over at the top, with one half of the loop moving upwards as the person moves upwards, and the other half moving downwards. Doubled rope technique halves the distance moved when pulling on the rope, but also theoretically halves the effort needed. However, this advantage can be largely lost, depending on how much friction there is at the top, and typically, the friction from a tree branch will remove most of the advantage, and will also damage the bark on the branch. As a result, various techniques have emerged to pull a sling or strap called a friction saver or cambium saver into position, which has metal rings for the rope to slide through instead, reducing the friction, and protecting the tree. Doubled rope technique also affects abseiling, since the descender does not see as much load, and therefore may generate too much friction (or too little with some auto-locking descenders). Doubled rope technique technique is used extensively by arborists to ascend trees, where it is contrasted with stationary rope technique, and was also historically used in mountaineering to descend cliffs, and sailing to descend a mast. This is primarily because of the reduced effort, since arborists often do not use leg power to prusik, and rely only on arm strength, while walking up the tree. They call this body thrusting. Although the person is attached at two ends of the same rope, there may only be a single rope being used. As a result, unless there is a backup line, this is still a variation of single rope technique.
Alternatively, doubled rope technique could refer to where the rope is looped over a high branch without being attached to it, and a double ascender is used for prusiking up both ends of the rope at the same time. While it would be possible to abseil using any descender that can use two ropes at the same time (such as a rack), it is more common to reconfigure the rope as a pull-through for abseiling. Once again, this is actually a variation of single rope technique, and is in fact also a stationary rope technique.
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