Carabiner Buying Guide
Carabiners are essential elements of any climbing safety chain. Whether clipping protection, building a belay or simply belaying a partner, the carabiner always has a role to play. This buying guide explains the differences between the various shapes and sizes of carabiner available, discusses how they are made and also how they're tested so you can make an informed decision about which to buy for different types of climbing.
Head this way for our full range of carabiners and quickdraws.
There are three main types of carabiner shape..
This uniform shape ensures that the load stays centred, thereby helping to avoid the dangers of cross loading. Oval screwgate carabiners are widely used on big wall and pulley set-ups. An oval wiregate is also great for racking nuts, allowing them to fan out evenly beneath the carabiner for easier selection.
'D' & Offset D
Adapted from the Oval shape, the original D has a straight back bar and symmetric curves to the gate. The focal point of the load is nearer to the back bar which increases the carabiner's strength slightly. Recently the D has been replaced as the versatile carabiner of choice by a non-symmetric variant, the 'offset' D. Like the standard D shape, this focuses the load along the back bar but a narrower lower section helps make the carabiner lighter. They can also generate a slightly larger gate opening. The angle of the upper curve is ideal for clipping through protection or bolts so this shape is the standard for quickdraws as well as general purpose use.
The HMS (short for the German “Halbmastwurf Sicherung”) is essentially a very large offset D. The extra size creates a wider and thicker top bar, which allows ropes to run very smoothly. For this reason many people will choose to belay with an HMS carabiner. The extra width and larger gate opening also allows for multiple ropes or knots (like the Munter hitch or two clove hitches) to be attached.
Simple straight gates are the classic all round non-locking option. They are commonly used in quickdraws, especially for clipping protection or bolts. Many solid gate carabiners now come with 'keylock' clean noses rather than a notched nose, helping to prevent irritating and potentially dangerous hang-ups where the gate and nose don't engage properly.
Bent gates give a slight advantage when clipping a rope; the rope is guided into the carabiner's basket by the curve of the gate. Bent gate carabiners are therefore often used on the lower end of quickdraws to facilitate quick clipping. Like straight gates, many bent gate carabiners will have 'keylock' clean noses.
Snap gates (straight, bent or wire) make sense for quickdraws where speed of clipping is crucial, but a locking carabiner adds security when belaying a partner or when building belay rigs. Screwgates are the most common form of locking gate and offer great value, but they do rely on the user to remember to do up the sheave every time. Keylock clean noses are increasingly common and help prevent snags.
When belaying it's important to use a carabiner with a generous top bar. Small, narrow-angled D shapes can exert too much friction on the rope and make belaying catchy and unpredictable. An HMS locking carabiner is ideal, though it's important to remember that screwgates must be locked manually every time. This explains why automatic locking HMS options are also popular. One of the other dangers when belaying is that the carabiner twists round and becomes cross-loaded across the gate. Specific belay carabiners that capture the belay loop can prevent this happening.
Constructing safe belay positions at the end of a pitch is a skill in itself. Locking carabiners (usually offset D shape screwgates) should be used to connect slings or the rope to protection. You will then often need to bring together a few slings and/or bights of rope into one hub. This central point will often demand a large HMS locking carabiner. The key is to have several screwgate carabiners on your harness to deal with all eventualities.
Quickdraws are made up of two carabiners joined together by high strength webbing. When climbing, one carabiner is clipped to a point of protection, for instance a bolt hanger or camming device. This carabiner is usually able to move freely within the sewn sling to reduce the 'pull' on the protection. The other carabiner is clipped to the rope. This end is often secured within the sling by a tight rubber 'tadpole' which prevents the carabiner from twisting, thus reducing the possibility of cross-loading and keeping it well positioned for clipping the rope. The sling increases the distance between protection and rope (hence why they're often called 'extenders'). This allows the rope to run more freely with less risk of dislodging the protection.
For traditional climbs, quickdraws with lightweight wiregate carabiners are the norm. The wiregate is especially useful on winter climbs as it won't freeze shut. Thinner, lighter slings also help cut the weight of your rack on the harness. Carrying a variety of lengths from 10-12cm (short) through 15-18cm (medium) and up to 25cm (long) allows you to manage the line of the rope on meandering trad routes and when crossing roofs. A rack of a dozen quickdraws will usually suffice for most pitches.
For sport climbs, quickdraws with sturdy solid gate carabiners are the norm. Chunky carabiners put up with constant abuse and regular falls. Wider slings are much easier to hold when working routes and hauling back to your highpoint. A straight gate makes bolt clipping easy while a bent gate facilitates rope clipping. 10-12cm lengths are fine for most straight-up routes, but it's also worth carrying a few longer sport draws for occasional use. A rack of a dozen quickdraws will suffice for most pitches but long european sport routes might require far more. Guidebooks will often give the number of bolts for any route so you can check you have enough before setting off.
For decades carabiners have been built by 'cold forging', whereby aluminium rod stock is bent into the required shape at room temperature. The results are very strong and consistent. However they lack the finesse of modern hot forged carabiners. Hot forging requires the heating of both rod stock and dies. Hot metal can be moved around by the dies, allowing the creation of more complex and tailored designs. Metal can be concentrated where it's needed and removed where it's not needed. This process allows 'I-Beam' profiles as well as enhanced radii on rope-bearing surfaces and even clean noses on wiregate carabiners. Hot forging can provide lighter weight units with no strength compromise
Once the carabiner has been forged and heat treated, it can be anodised. Anodising thickens the natural oxide layer that covers aluminium alloys exposed to air. This process increases wear resistance and allows the durable application of colour.
The DMM video below takes you through much of the manufacture process of a carabiner.
Every climbing carabiner is required to display its strength ratings on the back bar. There are three statistics quoted; major axis, minor axis and gate open.
- Major axis strength is measured for a load along the back bar with the gate closed (the normal mode).
- Minor axis strength is measured for a load across the gate with the gate closed.
- Gate open strength is measured for a load along the back bar with the gate open.
Carabiners are rated in kiloNewtons (kN), a measure of force. It's hard to visualise this dynamic measurement; if your carabiner is rated to 25kN along the major axis, what does that mean? A 25kN rating is roughly equivalent to a 2500kg mass under the influence of gravity. Therefore the carabiner would hold a static load of 2.5 metric tons.
Carabiners are tested on a pull rig which gradually ramps up the pressure until the carabiner breaks. The breaking force is recorded; the EN-12275 standard requires Basic and HMS carabiners to have major axis strength of 20kN and minor axis strength of 7kN.
Go to 20:40 on the DMM video to watch a carabiner being stress tested!
DMM and Black Diamond are two companies that use the 3 Sigma standard to establish their stated rating strength. Testing a large quantity of carabiners to breaking point, they derive a normally distributed bell-shaped curve. By quoting a breaking strain value that is 3 standard deviations (3 sigma) less than the actual average figure derived in testing, it is known that 99.87% of all carabiners produced will equal or exceed the stated breaking strain.
Buying Carabiners & Quickdraws
We hope this buying guide has helped explain the differences between different kinds of carabiner and what kinds of unit might be used for different types of climbing. To get a real feel for which models will suit you best it's always a good idea to hold them in-store, check how responsive the gate feels, whether it's the right size and shape and simply whether you'll enjoy clipping them on your next climb.
Carabiners & Quickdraws