In the absence of natural protection, climbers use artificial protection devices. These devices include chocks (artificial chockstones), bolts, and pi-tons. In most cases, the leader will use a chock or bolt, although pitons still have their uses. On a climb, the leader secures the piece of protection in the rock, providing a point of attachment for a runner, which is then connected to the climbing rope using carabiners.
Chockcraft—the art of placing and removing chocks—is the preferred technique for protecting climbs. This supports the ethic of clean climbing, which is climbing that does not permanently alter the environment. Chocks are relatively easy to place and to remove and, unlike bolts and pitons, leave no scars on the rock.
Chocks are either wedges or cams (fig. 10-6). Wedges hold a fall by wedging against a constriction in a crack or against another wedge. Cams hold a fall by rotating slightly within a crack, creating a camming action that jams the chock against the rock.
Wedges and cams are either passive or spring-loaded. Passive wedges and cams are single pieces of metal, without moving parts, that are simply placed firmly in an appropriate location in the rock. Spring-loaded wedges and cams are chocks with moving parts that are retracted in order to fit them into a spot, then allowed to open fully again to hold them in that place.
To become proficient at chockcraft, a climber learns the strengths and weaknesses of different types of chocks and learns to place them correctly.
The lead climber should know the breaking strength of each chock, information published by manufacturers or independent testers. Larger chocks are usually heavier and stronger than smaller chocks, and therefore have a higher breaking strength. Some smaller chocks aren't even meant to hold a fall, but are strong enough to support a climber's weight in aid climbing.
All chocks are designed to use in a rock feature—usually a crack, sometimes a pocket. Before placing a chock, the climber inspects the rock, both to judge its soundness and to decide what chock to use.
DOUBLE FISHERMAN'S KNOT
Fig. 10-6. Examples of artificial protection: a, passive wedge; b, passive cam; c, spring-loaded wedge; d, spring-loaded cam.
The type of rock and its condition help indicate whether the chock will hold a fall. Specifically, chocks tend to hold well in solid rock. Crumbling or deteriorating rock is unreliable, and should be avoided.
If you're thinking of putting a piece of protection behind a rock flake, remember the hollow-sound test. Hit it with the palm of one hand, and if you hear a hollow sound, don't use the flake. Under load, it takes only a slight movement of the rock for the chock to lose its grip and fail.
The size, shape, and orientation of the crack or pocket determines what chock to use. Does the crack or pocket flare outward, flare inward, or have parallel sides? Is it shallow or deep? Is it vertical or horizontal? Some types of chocks work well in one situation, not so well in another.
Some other general considerations in placing chocks:
• Learn to estimate the right chock size for a particular placement. The better the estimate, the faster the placement—and the less chance the climber will tire and fall.
• Choose the best chock, not necessarily the largest one possible. A larger chock usually will hold a harder fall, but first decide if it actually provides the soundest protection or if a smaller piece would be more secure.
• Decide whether a particular chock is likely to be adequate, based on the characteristics of the rock and the magnitude of a possible fall. If not, reinforce it with another chock or find a better placement.
• Check out every chock after it's in place. Look to see that it's placed correctly. Tug on it to help determine the strength and security of the placement, especially in the likely direction of pull.
• Guard against the chock being dislodged by rope movement. A runner is usually attached, with carabiners, between the chock and the rope. This helps reduce the effect of rope movement. Wired chocks are more affected by rope movement and have a greater tendency to rotate out of place.
• Guard against the chock being dislodged by an outward or upward pull. Many chock placements are one-directional; they will take a load in only one direction. If a one-directional placement could come under a load from multiple directions, make it multidirectional by placing opposing chocks. (This procedure gets a full explanation later in this chapter.)
• Remember the climber who will be following behind you and removing the protection. Make your placements secure, but also try to make them reasonably easy to remove.
A climber's high-priced pieces of protection won't do any good until they're connected to the rope. So every chock must include some type of sling as a part of the attachment system from the chock to the rope. The sling is usually made from accessory cord, tubular webbing, or wire cable.
Smaller chocks usually come with a wire cable sling, which is much stronger than cord or webbing of the same size. The ends of the cable are swaged together. Larger chocks come pre-drillcd with holes for accessory cord, which is usually added by the climber. Some chocks come pre-slung with tubular webbing.
There is a bonus advantage to using wire cable with passive wedges, such as Black Diamond (formerly Chouinard) Stopper nuts or Wild Country Stones. The wire's relative stiffness makes the wedges easier to handle and to place.
However, with passive camming chocks, such as Black Diamond Hexentric nuts, it's better to have accessory cord, providing it's strong enough. The cord permits the chock to rotate and cam freely as it's meant to do. Most modern hexes arc drilled to accept 5.5-millimeter accessory cord.
For many years, climbers used 6- to 9-millimeter nylon cord and 1 -inch nylon webbing to make chock slings. Nylon is durable and inexpensive but requires relatively larger diameters for strength, creating bulky and heavy chock slings.
An alternative fiber called Kevlar came into use for accessory cord. Kevlar cord at 5.5 millimeters in diameter is smaller, lighter, and stronger than nylon. However, Kevlar cord is weakened by repeated bending. Consequently, the manufacturer recommends it only for tying chock slings, because these slings are knotted just once and are not subjected to repeated bending.
A new fiber, Spectra, is even lighter, stronger, and more abrasion resistant than Kevlar. For use as chock slings, the Spectra fiber is used in 5.5-milli-meter cord or 9/i6-inch webbing.
Here are some things to keep in mind when attaching accessory cord as a sling to a chock:
• Inspect the holes that are drilled in the chock for the cord. They should have rounded edges to reduce the chance the sling could be cut under stress.
• Tie the ends of the cord together with a double fisherman's knot. Check it frequently in use to be sure it stays tight.
• Determine the right length for the sling. A sling is usually between 8 and 14 inches long, and some manufacturers provide information on how much sling material is needed for chocks of different sizes. One caution: If you make a chock sling too long, it could hang down far enough to interfere with footwork during climbing.
Out on a climb, no one will mention anything called a "passive wedging chock." Out there, passive wedging chocks go by a lot of catchier names: brands such as Stoppers, Stones, and RPs, and terms such as nuts, steel nuts, micronuts, tapers, and just plain chocks.
Wedging chocks are tapered down from top to bottom so they will fit into a constriction in a crack. They have a wide side and a narrow side, and are strongest when the wide surface area is touching the rock (fig. 10-7). The object is to get the greatest possible contact between chock and rock. Many wedging chocks, especially the smaller sizes, are not designed to be placed with the narrow side in contact with the rock.
A passive wedging chock has no moving parts to hold it in place. It sits passively in a constricting crack until it takes a load—such as a leader fall.
Fig. 10-7. Wide-side and narrow-side placement of passive wedging chocks: a, wide sides are in contact with the rock, a stronger placement; b, narrow sides are in contact with the rock, a weaker placement.
Then the chock wedges into the crack, generating expansion forces and increased friction. It holds tight.
Though they all taper, there are variations in the shapes of wedging chocks (fig. 10-8). Manufacturers try subtle changes in design to improve performance, and new designs continue to appear.
Some wedging chocks are straight-sided, some
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