Key takeaways
- A nut (chock/stopper) is passive protection — a shaped metal wedge on a wire, slotted into a crack.
- It works in tapering constrictions: a downward pull wedges it tighter against the narrowing crack.
- With no moving parts, nuts are simple, light, cheap, and reliable in good placements.
- They complement cams: nuts excel in tapering cracks, cams in parallel ones.
Originally from machine nuts threaded on slings by early climbers.
What a nut is
A nut — also called a chock or stopper — is a piece of passive, removable protection: a shaped metal wedge on a wire or cord. You slot it into a tapering constriction in a crack so that a downward pull (a fall) wedges it tighter into the narrowing rock. With no moving parts, it’s the simplest form of trad protection. (The name comes from early climbers threading machine nuts onto slings.)
How to place one
Find where a crack narrows, slot a correctly sized nut above the narrowing so it can’t pull through downward, and give it a firm downward tug to seat it. A good placement has solid rock contact on both sides and is set so a fall pulls it deeper into the constriction, not out.
Leading a crack that pinches down, a trad climber eyes the constriction, slots a nut just above it, tugs it to set it solidly, clips the rope, and climbs on — a fast, light placement exactly where the tapering crack lets a passive nut shine. Their follower frees it with a nut tool.
Nuts vs cams
Nuts are passive and excel in tapering cracks; cams are active and excel in parallel cracks. Nuts are lighter and cheaper; cams place faster in more situations. Trad climbers carry both — see cams vs nuts — and use them to build anchors.
The bottom line
A nut is passive trad protection at its simplest: a metal wedge on a wire that you slot into a tapering crack, where a fall only wedges it tighter. Light, cheap, and reliable with no moving parts, nuts shine in constrictions where cams can't, which is why trad climbers carry both and pick the right one for each placement (and a nut tool to free stuck ones).
Frequently asked questions
What is a nut in climbing?
A nut, also called a chock or stopper, is a piece of passive (no moving parts) removable climbing protection: a shaped metal wedge attached to a wire or cord. You slot it into a tapering constriction in a crack, and when weighted by a fall, the downward pull wedges it tighter into the narrowing crack, holding the fall.
How do you place a nut?
Find a spot in a crack where it narrows (a constriction), and slot a nut of the right size above the narrowing so it sits where it can't pull through downward. Give it a firm downward tug to seat it. A good nut placement has solid rock contact on both sides and is set so the direction of a fall pulls it deeper into the constriction, not out.
What's the difference between a nut and a cam?
A nut is passive — a fixed wedge that relies on a tapering crack to hold it — while a cam (SLCD) is active, with spring-loaded lobes that grip parallel-sided cracks. Nuts are lighter, cheaper, and excellent in constrictions; cams handle parallel cracks and place faster but cost more. Trad climbers carry both and choose the right tool for each crack. See our cams vs nuts comparison.
Sources
- Protection & trad gear — American Alpine Club
- Climbing protection standards — UIAA