Nut

A nut, sometimes called a stopper or chock, is a small tapered piece of metal threaded on a wire loop that a climber wedges into a narrowing crack or pocket. Unlike a cam, a nut has no moving parts, it relies purely on its tapered shape jamming into a constriction to resist an outward or downward pull.

Because they are simple and light, nuts are a cheaper and lighter way to protect many crack sizes compared with a full cam rack, and a set of a dozen or so nuts covers a wide range of crack widths. They do take more practice to place well than cams, since finding the right constriction and seating the nut securely by hand or with a nut tool is more of a feel based skill.

A nut placed in a crack that flares outward, rather than narrowing, can pull straight through under load, so learning to read the rock and test placements with a firm tug is an important skill to build under supervision. Nuts also double as a lightweight option for building anchors alongside cams and slings on trad routes.