INTRODUCTION

Carabiners are everywhere nowadays. From your harness at the top of a cell tower, to the anchor on a multipitch rock climb, and even to your keys hanging off your belt loop, there is no shortage of carabiner exposure these days. But do you know just how many types of carabiners there are? The different shapes? Materials? Uses? 

In this post, we’ll discuss carabiners with a little more depth to aid in your next carabiner purchase to ensure that you are getting the right tool for the job.

CARABINER SHAPES

First off, let’s discuss carabiner shapes and why those shapes are important. Despite the myriad variations that exist nowadays, there are four basic shapes to carabiners: oval, D, off-set D (aka asymmetrical D), and HMS (or pear-shaped). Each shape does its own job of distributing the load in a certain manner or keeping the carabiner in a certain position. 

For example, the load in an oval shaped carabiner will be distributed straight down the middle of the carabiner. This is strong, but the shape will never keep the load closer to the spine, which is far stronger. The shape also makes the carabiner prone to rotate or become cross-loaded, which is when the carabiner sits perpendicular to its proper orientation and the load is placed on both the gate and the spine.

 With a D shaped carabiner, the load is directed away from the gate and toward the spine, making it an ideal shape for most applications, whether recreational or industrial. By redirecting the load as it does, this design also helps to prevent cross-loading. 

The offset-D performs the same function as the D, but the design is altered in a way that allows the gate to open wider, which can be important depending on the carabiner’s intended purpose. You don’t want to try attaching your bag to a 2-inch beam only to find that the carabiner’s gate only opens to 1 inch.

Last but not least is the HMS carabiner, which is primarily used in recreational or rescue settings. HMS is an abbreviation for the German phrase “Halbmastwurf sicherung”, which roughly translates to “half clove hitch belay” or “munter hitch”. When switching from raising to lower with a munter hitch, the bulky hitch will flip through the carabiner to allow the rope to feed as needed. The pear shape of these carabiners is particularly helpful here in that it is wide enough to allow this bulky hitch to flip through, while a standard oval or D carabiner might be too small, blocking the hitch from flipping through as desired. These carabiners are often used with recreational climbers for belay device connections or as a master point clip at an anchor. They serve their purpose well, but their shape allows them to rotate and possibly become cross-loaded as well.

CARABINER GATES

Now, in addition to body shape, a particularly noteworthy component of a carabiner is its gate. There are a variety of different gates, but we’ll start with one of the most important distinctions: does it lock or not? Non-locking carabiners are all over the recreational world, and are typically what you will see with accessory carabiners as well. Locking carabiners, and particularly auto-locking carabiners are the norm in the industrial world in North America but also have their place recreationally with anchors and important attachment points. They will typically have a mechanism with a locking sleeve over the gate that, when activated, prevents the gate from opening accidentally. They help clip tower climbers to their objective, attach loads in rigging scenarios, and are the typical connectors between a climber and their descending device or belay device.

With non-locking carabiners, the gate designs are quite basic: is the gate straight or bent? This really only has any weight in your decision making when doing something like rock climbing. Straight and bent gates (and even wire gates) can be equally strong, but the bent gate carabiners are easier to open when clipping a rope through it. 

With locking carabiners, the gate designs just keep getting more and more innovative and interesting over the years. Is it a twist lock? A screw lock? A pinch lock? Does it automatically lock? Can it be opened with a glove? One handed? And so many more. In the North American industrial world, autolocking carabiners are required, and they must meet certain specifications to be either NFPA or ANSI rated. While there are many more details that go into the ANSI or NFPA rating process, the numbers below are the basics that rated carabiners fall into:

NFPA:T rated (Technical Use) - 27kn with gate closed, 7kn with gate open, 7 kn along the minor axis 

G rated (General Use) - 40kn with gate closed, 11kn with gate open, and 11kn along the minor axis

ANSI: 22kn with autolocking gate/device that breaks at 16kN

LOCKING MECHANISMS

One thing to keep in mind with locking carabiners is the locking mechanism. If you are rock climbing and can use both bare hands at an anchor, your needs are going to be much different from someone on a cell tower working with gloves on. So, will you be using this with bare hands? Gloves? Can you use both hands to open it? Do you need to be able to do it one handed? These are all important questions to ask to make sure you’re getting what you need. The most common locking mechanisms are screw locks, twist locks, and tri-action locks, all descriptive and to the point names. A screw lock features a mechanism in which you screw or unscrew a piece on the gate which will either lock or unlock the carabiner. The twist lock is an autolocking feature which simply requires you to twist the gate before it can be opened. Once let go, it springs back into place and re-locks itself.

The tri-action locks are auto-locking carabiners with much like the twist gate, with one extra step in the beginning requiring you to slide the gate sleeve up or down before twisting. While these are the primary mechanisms, there are others out there now: the ball lock (pinch the knobs together to unlock and open), pinch lock (pinch the angles and open), the wire lock (slide the wire down and open), and more. Skylotec’s Double-O Tri is a tri-action locker which can be twisted in both directions to open, which is a unique feature that allows you to handle it more easily whether left or right handed. 

CARABINER MARKINGS

So, how do you know if your carabiner is ANSI or NFPA rated without looking it up online? Somewhere on the carabiner it will say so. This is a good point to talk about the markings on your carabiners. If you inspect it on all sides, you will find all of this valuable information. It will have the strength ratings on the side indicating the strength of the carabiner loaded along the spine with the gate closed, with the gate open, and if cross-loaded. In addition to these numbers, it will typically say if the carabiner has been tested to meet NFPA, CE, UIAA, UL, or ANSI standards. Look all around the carabiner for this information as it may be on the side of the spine, on the rear of the spine, on the upper hook, on the bottom, etc.

ALUMINUM vs. STEEL

One of the talks often had in the industrial world regards steel carabiners vs aluminum carabiners. In the recreational world, aluminum carabiners are used without a second thought. But, they are not being exposed to the loads that can often be found in the industrial world, and the thought of a 5,000 lb. load on aluminum scares some people. Thinking about that same load applied to sturdy, heavy steel is more comforting, which is understandable. However, design and engineering have come a long way, and you will find that many aluminum carabiners are rated well above the 22kN (5,000 lbs) strength required by ANSI connectors. Where many aluminum carabiners do not meet the strict criteria is with the autolocking gate strength. There are aluminum carabiners that meet the 16kN break strength on the gate, but the number is definitely fewer. Here at ASK, we've seen that a local favorite is the Petzl Bm'd.

Steel carabiners are well trusted for their strength and durability, with Pro-Climb’s steel carabiners rated up to 45 kN and Petzl’s Oxan carabiner up to 38 kN, but they are noticeably heavier than aluminum. For example, the Petzl Oxan and Petzl Bm’d are both NFPA and ANSI rated, but the stainless steel Oxan weighs about 1.86 times more than the aluminum Bm’d. The weight differences are even greater if not necessarily needing those ANSI requirements. 

One thing to be mindful of with aluminum is that while it is strong, it is softer than steel. A carabiner that sees repeated use can start to develop grooves from rope running through it or knicks at regular attachment points. Edelrid makes a carabiner specifically to deal with this problem in the recreational world that is made of aluminum but has steel guards where the rope would run to protect the carabiner from excessive wear and grooving. Regardless of what material carabiner you have, remember to always inspect your gear for wear and tear. 

CONCLUSION

While we could go even deeper into carabiner talk (what’s with the H-frame? Why do some have a notch on the tip of the hook? We talked about NFPA and ANSI, but what about UIAA, CE, etc.?), this is a good stopping point. If you work in the industrial world in North America, those NFPA and ANSI ratings will be particularly important to you. You know those aluminum carabiners are not equivalent to soda cans on your harness, and hopefully now you are aware of the basic information to help you find the best for your specific job when shopping for your next carabiners. And if you still aren’t sure? We give a damn…so ASK us! We’ll get you going in the right direction.

Gear up, stay safe, and stay gritty!