In rock climbing, a nut (or chock or chockstone) is a metal wedge threaded on a wire that climbers use for protection by wedging it into a crack in the rock. Quickdraws are clipped to the nut wire by the ascending climber and the rope threads through the quickdraw. Nuts come in a variety of sizes and styles, and several different brands are made by competing manufacturers. Most nuts are made of aluminum. Larger nuts may be threaded on Dyneema cord instead of wire, but this has become unusual. The very smallest nuts are known as micronuts and may be made of brass or other metal, and typically have their wires soldered into them, instead of looped through drilled holes. They are mostly used in aid climbing, and their value as protection, arresting a climber's fall, is marginal because of both their low breaking strength and their tiny surface area (the HB 0 measures about 4 x 7 x 2.5 mm) in contact with the rock, though this can be offset if several are placed at a time. Other names used include RPs (the brand name of the first commercially available micronuts) and brassies. They are available from several manufacturers in a variety of styles. British climbers in the 1950s and 1960s were the first to use nuts as climbing protection. In addition to using pitons, they picked up machine nuts from the side of railway tracks, climbed with them in their pockets, and used them as artificial chocks. This developed to the point where they drilled the thread from the middle, threaded them with slings, and used them in cracks. Nuts or chockstones are named after natural stones occasionally found wedged into cracks. Climbers eventually realized they could insert their own found pebble into a suitable crack. In an article called "Artificial Aids in Mountaineering" dated Oct-Dec 1956, G Sutton wrote about jammed knots for direct aid. He also compared the use of slings, chocks (rocks) and jammed knots to artificial climbing (aid climbing) and that "there should be no illusion that the use of a chockstone is in any way more admirable than that of a piton." By 1967 Royal Robbins saw the need for clean climbing and put up Nutcracker, an all nut protected 6 pitch climb, on the Manure Pile(Ranger Rock),Yosemite. In 1972, when clean climbing became an issue in the US, Yvon Chouinard began manufacturing