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A Climber’s Guide to Carabiners

Carabiners are the unsung heroes of the climbing world.

They get beat up and save thousands of climbers’ lives day after day, all without the slightest nod of gratitude or appreciation for their ingenious form and function.

A carabiner is a loop of metal with a spring-loaded gate that opens and shuts. Despite what you might think if you were to stand at the entrance of an outdoor sporting goods store, a carabiner’s essential purpose isn’t actually to clip a water bottle to the outside of a backpack, or keys to a belt loop, or even a rope leash to Denali the dog’s collar. Carabiners serve much higher causes. They allow climbers to perform virtually every task, from clipping their ropes into protection, to racking gear, to holding falls. They allow us to move in the vertical world safely, quickly and efficiently.

The first carabiner was invented on the eve of World War I by the German climber Otto Herzog. Around 1921, the first carabiner for climbers, weighing 4.5 ounces, was produced. Today, thanks to advances in design and metalworking, full-strength carabiners can weigh just a single ounce.

Also today, you can find dozens and dozens of designs, shapes and models of carabiners that all serve particular purposes in the climbing world. Here’s a guide to everything you need to know about choosing carabiners for climbing.

Parts of the Carabiner


The part of the carabiner that opens and snaps shut.

The long side of the carabiner opposite the gate.

The part of the carabiner into which the gate snaps, closing the loop.

Often the more prominent of the two bends in the carabiner shape, and where the rope or gear sits when clipped.

Carabiner Terms

Gate opening
How wide the gate opens. This can determine several functions, from how easy the carabiner is to clip with a rope, to how much gear can be racked on the carabiner.

A term to differentiate “normal” sized carabiners versus the new generation of small or mini-carabiners such as the Petzl Ange S or the Metolius FS Mini.

Carabiners are meant to be loaded along their longitudes/lengths. When they are loaded latitudinally, from gate to spine, that is what is referred to as “cross loading” and it is a potentially dangerous situation. Carabiners are roughly three to four times weaker in a cross-loaded configuration, and precautions should be taken to avoid it.

This is a super-dangerous situation in which a carabiner accidentally becomes hung on a bolt or even a sling only by its nose. More dangerous than cross-loading, a nose-hooked carabiner can actually break. It’s a relatively rare occurrence, but it’s been known to happen.



There are essentially two styles of carabiner: steel and aluminum. Steel carabiners are extremely durable and relatively heavy. Aluminum carabiners are extremely lightweight and durable enough for years of use, but will wear out much more quickly than steel. Steel carabiners are reserved for high-use situations such as quickdraws and anchors in a gym, or “perma-draws” at certain crags where that’s allowed. Aluminum carabiners should never be fixed on routes, whether on draws or at lower-off anchors.

Understanding Strength

It’s safe to say that any carabiner made for climbing purposes is more than strong enough for its intended, proper use. In other words, there is no real need to worry about the carabiner’s strength rating, which is stamped into the spine of every carabiner. Look on a carabiner spine, and you will often see two numbers with corresponding arrows. One number is the carabiner’s strength rating along its longitude, and the other is the carabiner’s strength when cross-loaded. Either way, strength won’t be a consideration when choosing carabiners; they will all be plenty strong enough so long as they are actual carabiners meant for rock climbing and not those little toy key-chain ones.

Shapes of Carabiners

binershapesOval Shape
The original shape of carabiner, ovals are still being produced by various companies. Their one and only benefit—aside from being cheaper—is the rather dubious claim to being able to rack more gear than other shapes of carabiners. Otherwise, they are weaker, heavier and harder to use.

Regular D-Shape
The second step forward in the evolution of the modern carabiner, regular D-shaped carabiners improved on Ovals by reducing weight and increasing strength.

Asymmetrical D-Shape
Now we’re talking! The offset D, or asymmetrical D-shaped carabiner is the most popular design because it is the lightest shape, strongest design and has a much larger gate opening than regular Ds, which improves functionality in everything from clipping to racking. These carabiners should comprise 99% of your rack.

Pear shape
This oversized design is reserved for locking carabiners to be used with belay/rappel devices.

Locking vs Non-locking

Carabiners can basically be divided into locking and non-locking. Non-locking carabiners are carabiners whose gates open when you push them open. Locking carabiners are different in that, depending on the design, they require you to take some extra step before you can push open the gate—basically, you have to “unlock” the carabiner to open it. Locking carabiners aren’t any stronger than non-locking carabiners, but they are safer in that it would be virtually impossible for a locking carabiner to unclip itself.

For some reason, climbers building their first trad racks end up buying something crazy like a dozen locking carabiners. There is no reason to ever own more than four locking carabiners. You need two medium-sized lockers for anchors, a pear-shaped locker for your belay/rappel device, and perhaps one more small locker if you use a belay/rappel device with auto-blocking capabilities while belaying a seconding climber, such as the Black Diamond ATC Guide or the Petzl Reverso.


Gate Options

Solid Gate
The most common type, solid gates are tubes of metal that open and snap shut using a separate spring mechanism.

NCPOL_D2Wire Gate
This type of gate is just a loop of bent wire that snaps shut under its own coiled tension. Wire gates look less strong than solid gates, but they often aren’t (in fact, some are now stronger). Because wires have less mass than solid gates, they are less likely to open under their own inertia. Typically, wire gates are lighter than solid gates. Whether or not they are easier to clip involves too many factors to generalize.

Gate Designs

Both solid- and wire-gate carabiners can come in the following designs:

Bent Gate
Carabiners with a slight bend in the gate are often reserved for the bottom, rope-clipping end of a quickdraw. The bent-gate design creates a wider gate opening, and is more ergonomic for pushing the rope through the gate when clipping on the go.

Straight Gate
Like its name says, a gate that’s straight. These carabiners are typically found on the bolt-end side of quickdraws, but that isn’t their only purpose. Straight gates are multi-purpose, all-around carabiners that can be great for racking cams and nuts, too.

Gate Closure

The way the gate attaches to the carabiners nose is super-important, not just in terms of strength but in terms of application and function in the vertical world. Typically, most carabiners contain a notch in the nose that hooks onto a tiny bar at the head of the gate. This is what keeps the carabiner closed under force. However, that notch can be problematic only in that it is prone to catching on things, from a rack of nuts to, worst case, the hanger of a bolt (thereby nose-hooking the carabiner).

CAMP USA Orbit CarabinerThis problem was solved with the invention of the “keylock” closure system, first introduced by the Petzl Spirit and now found on many other brands and models. A keylock is where the gate inserts like a jigsaw piece into the nose of the carabiner. The benefit to this design didn’t just make the Petzl Spirit suited to racking a set of nuts, but it also prevented nose-hooking on bolt hangers.

Keylock designs used to be only found on solid-gate carabiners. But today, there are a few wire-gate carabiners that have employed inventive solutions to create keylock-style functionality but with a wire gate. Check out the Black Diamond HoodWire or the Petzl Ange L.

What you need to know: keylock carabiners are the best carabiners for racking gear, especially nuts, and are less likely to be nose-hooked on bolt hangers or slings.

Locking Gates

There are a number of styles of lockers on today’s market, but the two most common are screw-gate and twist-lock and/or auto-lock. Screw gates tend to require two hands to operate: you hold the carabiner with one hand while you screw a sleeve down so that the gate can’t open. Twist-lock or auto-locking carabiners can be operated and opened with one hand, usually through a two-part motion (i.e., press down and twist open).

Size and Weight

Carabiners today come in a variety of sizes and weights. After choosing the style of gate, size and weight are the second and third most important considerations when choosing carabiners.

Weight matters for obvious reasons in a sport where you’re constantly fighting gravity for every upward inch. Though all carabiners are generally quite light, add up the weight of 50 of them for a big-wall rack, and a few grams here and there begin to add up. Even on a long 50-meter sport-climbing onsight attempt, you will feel a huge difference between 30 heavy quickdraws, and 30 super-light ones.

Size matters not only because it affects weight, but also function: smaller carabiners will generally be harder to clip. They will also hold fewer pieces of gear and fewer knots.

In the last 10 years, manufacturers raced to create the first sub-one-ounce carabiner, and a number of companies reached that goal, largely by making the carabiner physically smaller. Today there are a few full-size carabiners right around that magical weight of one ounce such as the CAMP Photon Wire and the Black Diamond Oz.


In general, your best bet is to get out there and try your hand at all the different options available. See if you prefer to clip wire gates over bent solid gates. Do small carabiners work for you, or do you think they’re too small? Above all, next time you find yourself mindlessly racking gear or clipping draws to bolts on your warm-up, take a moment to stop and appreciate your carabiners. Without them, we wouldn’t be able to do what we do.


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