Best Locking Carabiners (2026): The Rating On the Spine Assumes One Direction

What the numbers actually mean

Every certified carabiner carries three figures, usually as small pictograms on the spine.

• Major axis, an arrow along the length. This is the big number, typically 20 to 30 kN, measured spine-to-spine with the gate closed. The Petzl Am D here is rated 27 kN.
• Minor axis, an arrow across the width. Usually 7 to 10 kN. This is cross-loading.
• Gate open, typically 6 to 9 kN.

The gap between those is the whole safety story. A carabiner rated 27 kN along the spine may hold only 8 kN across it, and about the same with the gate held open. That is not a defect; it is how the shape works. Load passes along the spine because the spine is the solid side.

So the failure modes are positional, not material.

Cross-loading happens when a carabiner rotates so the load runs across it rather than along it — very commonly where a belay device or a sling twists in the basket. Many belay carabiners carry a captive bar or a rubber keeper specifically to stop this rotation.

Gate-open loading happens when a gate is pressed against rock, or a stiff sling holds it ajar, or vibration flutters it. A carabiner with its gate open is a hook.

Nose-hooking is when the nose catches on a bolt hanger or a sling and takes the load on the tip. This is what the keylock nose exists to prevent: a smooth notchless nose that cannot hook, instead of the traditional hooked nose with a pin.

Locking mechanism and shape

Screwgate is a sleeve you turn by hand. It is simple, cheap, lightweight, has nothing to seize up, and it is only locked if you remember to lock it. For anchors and rigging where you check everything deliberately, it is excellent. For a belay carabiner you handle constantly under stress, the fact that it can be left unlocked is the argument against it.

Auto-locking mechanisms lock themselves when released. Petzl's names are worth knowing because they come up constantly: Twist-Lock (twist only), Triact-Lock (lift then twist), Ball-Lock (push a button then twist). More actions means harder to open by accident, and harder to open with cold or gloved hands.

Then shape, which decides what it is for.

• Pear or HMS, wide at the top. The width accommodates a Munter hitch and lets a belay device sit properly. The BD RockLock here is the large version of this and is a belay and rappel carabiner.
• Asymmetric D, the most common shape. It pushes the load toward the spine, which is why it gives the best strength for the weight. The Petzl Am D is this, at 70 to 75 grams for 27 kN.
• Oval, symmetrical. It is weaker than a D for the same weight, and you choose it anyway because the uniform shape stops gear shifting inside it. That makes it the shape for pulleys, aid climbing and racking, where predictable position matters more than strength.

For canyoneering specifically, add water and grit to all of this. Sand works into screw threads and auto-locking mechanisms alike, so anything that goes in a canyon gets rinsed in fresh water, and a gate that grinds is telling you something.

Inspection and retirement

Check the gate every time. It should snap shut cleanly under its own spring, and the lock should run freely. A gate that is slow, gritty or does not close fully is a carabiner to retire, and in canyoneering that is usually sand in the hinge.

Rinse in fresh water after every canyon. Then work the gate while it dries. Salt and grit wear both the hinge and the locking threads.

Look for grooving. Ropes wear a channel into aluminium over time, especially on rappel carabiners. A groove you can catch a fingernail in has removed material from the loaded side, and that one is done.

Retire after a significant drop. A carabiner dropped from height onto rock can carry invisible microfractures. The fact that it looks fine is not evidence. They are cheap and you are not.

Do not lubricate with anything oily that will transfer to a rope. A dry lubricant or graphite on the hinge only, if anything.

Mind the age of slings and ropes too. Metal has no fixed shelf life but the textiles it connects to do, and nylon degrades with UV and age whether or not it has been used.

Mark your gear. Shared canyon kit gets mixed up, and knowing the history of a specific carabiner is part of knowing whether to trust it.