Anchors are natural or constructed objects to which a rigging system is secured. Most anchors such as trees, chockstones, and bolts remain in place after a group finishes using them, but some systems may be retrieved.
Natural anchors are pre-existing natural features such as rocks and trees that can be used directly or only slightly modified or improved to support a rigging system. These types of anchors are generally preferred to artificial anchors when practical because using them usually results in lower environmental impact.
When available, trees usually make excellent anchors. To use a tree as an anchor for a fixed rope, the most common rigging method is to wrap the rope around the tree a number of times to form a tensionless hitch. When the rope must be retrieved from the bottom of a rappel, it is not advisable to simply deploy rope on either side of the tree as the retrieval process will cause the rope to saw into the tree bark which can seriously injure the tree. Instead, the most common solution is to attach an anchor ring to the tree with webbing, use the anchor ring for rigging, and then leave the webbing and anchor ring behind. It is common for canyoneers to find and, following inspection, use webbing and anchor rings left by prior groups. To attach an anchor ring to a tree with webbing, a frost knot can often be a good choice, or a wrap 3 pull 2 can provide additional strength.
Chockstones are often similar to trees in that they can provide a very strong natural anchor while being relatively abundant in some areas. Anchor rings are usually attached to chockstones by webbing in similar ways as for trees.
Knot chocks are formed by creating a large knot of rope or webbing behind a constriction such that when the rope or webbing attached to the knot is pulled forward, it is unable to pass through the constriction.
Rock chocks are formed by tying webbing or rope around a rock behind a constriction that is too small for the rock to fit through.
Artificial anchors generally involve an irreversible modification of one or more natural features to allow an easier or more convenient rigging and descent. The most common form of artificial anchors are pairs of bolts and bolt hangers which form a redundant two-bolt anchor with connective webbing, though much older piton anchors may still be found in some areas. New bolts should generally only be placed by experienced people following good bolting techinques on routes they are familiar with. When replacing webbing on standard hangers, one may wish to consider the tradeoffs of webbing on bolt hangers.
Transient anchors involve the use of a tool or technique to create a temporary anchor that is intended to be dismantled shortly after being used, often from the bottom of a rappel. People unaccustomed to these methods often find them surprising. Some better-known transient anchors include: