Carabiners Explained
Types, gates, shapes, materials, and kN ratings — the complete reference for understanding climbing carabiners. From quickdraws to belay lockers.
A carabiner ("biner") is a metal loop with a spring-loaded gate, used to connect ropes, slings, and gear to anchors and other carabiners. They are the building block of all roped climbing systems — every belay device, every quickdraw, every anchor uses carabiners. Understanding the differences between types saves both money and weight.
This page covers the four major variables: type (locking vs non-locking), gate style, shape, and material. Plus how to read kN ratings stamped on every carabiner.
1. Locking vs Non-Locking
Locking carabiners
Gate locks closed via screw, twist, or magnet — used for safety-critical connections (belay device to harness, anchor connections, rappel setups). Required by most gym belay licences.
Non-locking carabiners
Spring gate only, no lock — used for quickdraws on sport routes, racking gear, and any non-load-critical connection where the gate is loaded closed by the rope.
2. Gate Types
The gate is the moving part of the carabiner that opens to clip in the rope or anchor. Different gate styles trade off speed, weight, and reliability.
Solid (straight) gate
Simple bent metal gate. Found on most non-locking carabiners and many lockers. Reliable, lightweight, easy to clip.
Wire gate
Bent stainless steel wire instead of solid metal. Lighter than solid gates and significantly less prone to "gate flutter" (the gate momentarily opening during a fall). Found on quickdraws.
Bent gate
Curved gate that makes one-handed clipping easier. Used on the "rope end" of quickdraws so the rope clips smoothly even under stress.
Screw gate (locker)
Threaded sleeve over the gate that you twist closed. Most common locker style — reliable, simple, requires user discipline to actually lock.
Auto-lock (twist-lock, triple-action)
Spring-loaded sleeve that locks automatically when released. Fast and idiot-proof for guides and frequent use; can be more prone to grit jamming.
Magnetic lock (Magnetron)
Magnets pull lock arms shut automatically. Fast one-handed operation. Black Diamond proprietary system.
3. Carabiner Shapes
Shape determines how loads are distributed across the carabiner. The right shape for your application matters more than the brand.
Pear / HMS
Wide rope-side basket designed for the bulkiness of a Munter hitch and ropes carrying multiple wraps. The standard belay carabiner shape.
Asymmetric D
Strong on the major axis, lighter than HMS, compact body. Standard for racking gear, anchor connections, and personal anchor systems.
Oval
Symmetric shape — gear loads consistently in either direction. Strong but heavy; used in aid climbing where racks of pulleys hang from a single carabiner.
D-shape (symmetric)
Older style. Largely replaced by asymmetric D for the same applications. Still common on budget gear.
For a deeper look at shape selection, see our carabiner shapes guide.
4. Materials
Aluminium alloy
The default for climbing carabiners — light, strong enough at typical climbing loads, affordable. Almost every carabiner in your rack is aluminium.
Steel
Heavy and almost indestructible. Used for industrial rope work and extreme-duration loads (e.g. via ferrata at high-traffic sites). Rarely seen in personal climbing gear.
I-beam construction
A lightening cut down the side of the carabiner spine. Reduces weight without significantly reducing strength. Standard on most modern lightweight gear.
5. Reading kN Ratings
Every certified climbing carabiner is stamped with three kN ratings (kilonewtons of force). 1 kN ≈ 100 kg of static weight, but climbing falls generate dynamic loads that briefly exceed normal weight by 2-5x.
Major axis (closed gate)
The strongest direction — load applied along the spine with the gate closed. Climbing carabiners must rate at least 20 kN here. Most rate 22-25 kN.
Minor axis (cross-loaded)
Loaded across the gate-and-spine width — much weaker. Standard rating is 7 kN; reaching this load means the carabiner is misused.
Open gate
Loaded along the major axis with the gate open. Standard rating is 7-10 kN. Why "gate flutter" matters: a gate momentarily open during a fall can fail at much lower forces.
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