Nut (climbing)

A selection of nuts and a nut removal tool.

In rock climbing, a nut (or chock or chockstone) is a metal wedge threaded on a wire, used for protection by wedging it into a crack in the rock. Nuts come in a variety of sizes and styles, and several different brands are made by competing manufacturers. Most nuts are made out of aluminum. Larger nuts may be threaded on Dyneema cord instead of wire, but this has become unusual. Nuts are related to, but not interchangeable with, Hexcentrics.

The very smallest nuts are known as micronuts and may be made of brass or other metal. They typically have their wires soldered into them, instead of looped through drilled holes in the nut. They are most commonly used in aid climbing, and their value as protection (ie arresting a climbers' fall) is generally considered marginal due to their relatively low breaking strength, and the tiny amount of surface area (the HB 0 measures about 4 x 7 x 2.5mm) in contact with the rock, though this may be offset somewhat by placing several of these nuts at a time if possible. 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 were the first to use nuts as climbing protection. Too poor to afford pitons, they picked up old machine nuts from along the side of railway tracks, climbed with them in their pockets, and used them as artificial chocks.

In 1972, when clean climbing was becoming an issue in the United States, Yvon Chouinard began manufacturing chocks made specifically for rock climbing, with the familiar wedge shape still in use today. Climbers like Henry Barber and John Stannard helped popularize their use, especially after it was discovered that a nut was lighter and generally easier to place while climbing, as well as being at least, if not more, secure than a well placed piton.

Nuts may be generically referred to as wires or stoppers. Stopper is a brand name of nut made by Black Diamond Equipment Ltd.