Which Locking Karabiner

November 8, 2008

Reading Time: 14 minutes.

Following on from the article How many screwgates should I carry, I thought I’d have a brief look at locking karabiners themselves.

The locking karabiner, more commonly known as the screwgate (SG), plays a central role in a climber’s safety, providing higher levels of security than a plain gate; especially important in situations where there is no room for failure (connecting you to your descender for example).

Lockers can be broken down into the following categories:-


For me, these are the most useful design and are generally an HMS shape. This shape is useful as it gives the user a great deal of space to clip ropes and slings, allowing you to use one connection rather than several. This of course is a double-edged sword, as using one connection rather than several means you’re totally dependant on its security, but in my mind as long as you can focus on (.i.e make sure it’s screwed up and oriented the correct way) then it’s good enough, and having just one krab to look after means you can do just that (compared to checking several lockers).

The strength of HMS or pear-shaped krabs is much lower than that of D shaped krabs, so it’s vital that you buy the strongest krabs you can find (forged), and perhaps avoid using them in high load/shock situations, such as on a runner (use a D shaped krab).

Personally I generally only carry two SG krabs on my harness, and they are both BIG, with one being clipped to my belay device, and the second loose for setting up belays (see How many screwgates should I carry).


This type of locking krab is usually a plain D shaped karabiner, the type of karabiner most people own, being not too large and not too small, strong but with an average capacity and internal space. Personally, I’d avoid this type of krab, and either buy up to a bigger more useful design or buy down to the krabs below.


IF you’ve got a specific purpose in mind for a locker, such as holding an item of gear that doesn’t require a large krab, such as a Gri-Gri or figure of eight, then a small lightweight screwgate is perfect, as it provides the same security as a full-sized design but at half the weight. The downside is that their internal space is small, so they can only be used with one or two knots (probably only one clove hitch).

This is an ideal karabiner to be used with a magic style plate.


Lockers come in two types, screwgates and auto lockers.


Screwgates have been around forever and require the user to manually lock them. The only thing to say about this design is that it’s not foolproof, and I tend to find if you want it to stay done up it comes undone, and visa versa!

The two main things to keep in mind is the strength of the collar itself and the collar’s ability not to become locked down. Both these things depend on the design and quality of the gate and collar, with either fault potentially being life-threatening.

Collar failure has led to numerous climbing fatalities (this is how it’s now thought that Tom Patey died) and is caused by the force being directed across the gate (pulling on the gate and spine, with the gate pin and collar taking the load). For this reason, it’s paramount that you’re using the latest screwgate designs, which feature much stronger collars than on older models, which could easily deform. For this reason, I’d recommend checking all main lockers, especially those used directly to your harness, and replace them with current models (Petzl, Dmm, BD etc).

Collar lockdown is caused by the tightening of the collar while under load (perhaps tightened on an abseil when still hanging from the rope). Once unloaded the collar will jam, and can only be unscrewed while loaded. In a self-rescue situation, this could prove very serious, and otherwise, it’s just annoying! To test your screwgate design won’t lock up, you should be able to tighten it down and still feel some play in the gate, as it will lockdown on the gate itself, not on the nose of the krab.

Auto Lockers

In the past auto-locking karabiners weren’t that popular, due to the fact they could be fiddly, heavy and prone to sticking. Modern designs are much better and provide a much higher level of protection compared to screwgates. Personally, I like auto lockers, and often prefer them over screwgates (but not in winter), as I can be 90% (bit not 100% meaning you still have to check!) that they are done up. There are several different types of auto lockers on the market, with Petzl having the broadest selection at the moment. Collars come in a plain twist to open and those that require you to push and twist. Both work well, but personally, I prefer the double-action collar.


Screwgates don’t always provide the level of security required, coming unscrewed rather too easily in some situations, especially if they are moving or rubbing against other objects.

For long term connections where security is paramount; such as a fixed rope, top-rope anchor or haul bag connection, a good alternative is the humble Maillon Rapide, a two-part ‘chain link’ with a screw collar rather than a gate. This provides the highest levels of security and strength, and come in dozens of different shapes, diameters and materials (usually alloy or steel).

It’s often worth having one spare maillon that can be used as a wrench on the others (by opening the collar and then clamping it back down on the other maillons collar), or carry a small spanner (rapping finger tape around the maillon’s collar also helps).

Steel maillons also make excellent rap rings, being cheap, strong and easy to carry (plus multi-purpose), with even the smallest designs providing adequate strength. Carry a couple on any long and committing route could save karabiners on the descent.

Another alternative is the good old back to back snap gates (two snap gates used together with their gates in opposition), which provides almost total security, and in the case of the lightest karabiners, actually weighs about the same as a screwgate. Personally, this is my choice for many things, as it’s simple, strong and gives great flexibility.

Oh yes and there’s always the cheekily named ‘Mexican’ screwgate… a plain gate with the gate gaffer taped shut!