Chock craft has been in use for many decades. A natural chockstone, having fallen and wedged in a crack, provides an excellent anchor point. Sometimes these chockstones are in unstable positions, but can be made into excellent anchors with little adjustment. Chock craft is an art that requires time and technique to master—simple in theory, but complex in practice. Imagination and resourcefulness are key principles to chock craft. The skilled climber must understand the application of mechanical advantage, vectors, and other forces that affect the belay chain in a fall.
a. Advantages. The advantages of using chocks are:
• Tactically quiet installation and recovery.
• Usually easy to retrieve and, unless severely damaged, are reusable.
• Easy to insert and remove.
• Minimal rock scarring as opposed to pitons.
• Sometimes can be placed where pitons cannot (expanding rock flakes where pitons would further weaken the rock).
b. Disadvantages. The disadvantages of using chocks are:
• May not fit in thin cracks, which may accept pitons.
• Often provide only one direction of pull.
• Practice and experience necessary to become proficient in proper placement.
c. Placement. The principles of placing chocks are to find a crack with a constriction at some point, place a chock of appropriate size above and behind the constriction, and set the chock by jerking down on the chock loop (Figure 5-15). Maximum surface contact with a tight fit is critical. Chocks are usually good for a single direction of pull.
(1) Avoid cracks that have crumbly (soft) or deteriorating rock, if possible. Some cracks may have loose rock, grass, and dirt, which should be removed before placing the chock. Look for a constriction point in the crack, then select a chock to fit it.
(2) When selecting a chock, choose one that has as much surface area as possible in contact with the rock. A chock resting on one small crystal or point of rock is likely to be unsafe. A chock that sticks partly out of the crack is avoided. Avoid poor protection. Ensure that the chock has a wire or runner long enough; extra ropes, cord, or webbing may be needed to extend the length of the runner.
(3) End weighting of the placement helps to keep the protection in position. A carabiner often provides enough weight
(4) Parallel-sided cracks without constrictions are a problem. Chocks designed to be used in this situation rely on camming principles to remain emplaced. Weighting the emplacement with extra hardware is often necessary to keep the chocks from dropping out.
(a) Emplace the wedge-shaped chock above and behind the constriction; seat it with a sharp downward tug.
(b) Place a camming chock with its narrow side into the crack, then rotate it to the attitude it will assume under load; seat it with a sharp downward tug.
Continue reading here: Springloaded Camming Device
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