Carabiners are the most indispensable tool in a climber’s arsenal. Used to quickly and safely connect components of a dynamic or static system, the carabiner is worth its weight in gold. Here is a run-down of the common types, shapes, and uses of a carabiner.
Carabiner Shapes: Carabiners come in a variety of shapes that dictate not only the name but also how you’ll use them.
Oval Carabiners: Popular tools in climbing quivers, oval carabiners are useful for aid climbing and make excellent top-rope anchors when used properly. They offer the weakest inherent strength due to the symmetrical nature of the carabiner, which puts equal pressure on both the spine and the gate when loaded. The symmetrical nature also can make them harder to handle.
D or Offset-D Carabiners: The strongest shape and the most popular carabiner on the market, D or Offset-D Carabiners carry most of the load on their spines, making them useful in almost all situations.
Pear-Shaped (HMS) Carabiners: Pear-shaped carabiners are often used for belaying. They usually offer a large rope-bearing surface and function well with modern belay devices. They are also called HMS carabiners, an abbreviation of the German Halbmastwurfsicherung, which means munter hitch belay, referring to the fact that they are uniquely suited to belaying with a munter hitch. For this reason carrying at least one HMS carabiner is a good idea in case you lose your belay device.
In situations where carabiner failure would be catastrophic and quick-release is not required, a locking carabiner is preferred. The primary use is at anchor points and for belay devices.
The simplest locking mechanism is the screwgate, which requires the climber to manually lock and unlock the carabiner. Many people prefer this method because it forces them to double-check their main anchor points, and due to its simplicity it is reliably secure even in icy conditions. Automatic locking carabiners will lock automatically, and are preferred by aid climbers for their speed and in situations when the rope will not be involved, such as clipping to an ascender or a Gri-Gri, but grit, sand, and ice may interfere with their operation. The newest locking system is a magnetic lock, which seems to have the benefit of automatic locking with none of the drawbacks.
Gate Types: Carabiners are available in standard gates as well as wire gates.
Wire Gates: While standard gates remain the go-to out of design necessity for all locking carabiners, many people have moved to wire gates for most uses in sport, ice, and trad climbing. Wire gates offer the advantage of being lighter, potentially safer (reduced gate flutter), and clear ice, snow, mud, and sand more easily. They are as strong or stronger than standard gates.
Standard Gates: Some people prefer standard gates in sport carabiners where a bend in the gate can make clipping easier (although some wire gates come bent as well).
Notchless Gates: Notchless have become more popular as they are much easier to use and don’t get hooked up on bolt hangers, wired nuts, or slings when unclipping. Many manufacturers now have designed notchless wire gates, which offer the best of both.
Weight: Nowadays carabiners are extremely lightweight. The race to making the lightest has gotten them down below 23 grams. Every ounce counts when you’re rock climbing, and if you have a big rack, buying lighter carabiners can save you pounds. However, you always have to consider usability—if your hands are too big to operate the carabiner easily, or if you will be climbing in the winter, regular-size carabiners are better.
Strength Ratings: All carabiners are rated on their spine for three strengths: along the major axis, gate closed; along the major axis, gate open; and along the minor axis. This strength is measured in kilonewtons, or kN. A single kN is about 224.8 foot-pounds of force, so a 25kN carabiner is quite strong, capable of holding more than 2 tons of force—that’s more than two grizzly bears. All carabiners are sufficiently strong along their major axis when closed for even the worst falls under normal circumstances. However, if the gate opens due to flutter or being pushed against the rock, the carabiner’s overall strength will significantly diminish. An 8Kn rating for open-gate strength is good, 10kN or better is ideal.
Pro Tip: Never cross-load your carabiner along the minor axis, as even normal falls can break them.