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The Best Locking Carabiners

Our fleet of locking carabiners ready to be reviewed!
By Ryan Huetter ⋅ Review Editor
Tuesday October 17, 2017
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The carabiner is an indispensable tool for rock and alpine climbers, mountaineers and backpackers, and even folks who just want to hang their keys on something. Carabiners come in both locking and non-locking varieties, and while both are used during a climbing outing, they each have their own unique applications. We took 10 popular locking carabiners and used them in a wide range of climbing and mountaineering situations to see which ones performed the best. We rated each carabiner on function, ease of locking and unlocking, compactness and weight as well as gate clearance and hang up. Keep reading to discover which contenders came out on top during our testing.

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Fall 2017 Update
We added back one our favorite value carabiners, the Mad Rock Ultra Tech. It tied for lightest locker with the Edelrid Pure Screw but is usually $3 cheaper. It's the locker we load up on for non belay applicaitons.

Best Overall Locking Carabiner

Petzl Attache

Petzl Attache
Editors' Choice Award

(25% off)
at Backcountry
See It

Wider opening
Red stripe to indicate biner is unlocked
Easy-to-open screw lock
Lacks durability of other carabiners

The Editors' Choice Award goes to the Petzl Attache. It was the only carabiner to score well in every category and the only light carabiner to excel in the overall scores. This carabiner performs exceptionally, no matter the situation. Its main drawback is the price.

Read review: Petzl Attache

Best Bang for the Buck

Black Diamond Rocklock Screwgate

Black Diamond Rocklock Screwgate
Best Buy Award

(25% off)
at Backcountry
See It

Keylock nose
Gate opening is large
Round stock for smoother rappelling/belaying
On the heavier side

The Best Buy Award goes to the Black Diamond Rock Lock, which scored very well in most categories, with the exception of weight and compactness. It was not only a top scorer, it was also among the cheapest carabiners at $11. It is an all around performer and is a durable choice for beginners and experts alike.

Read review: Black Diamond Rock Lock

Top Pick for Belaying

DMM Belay Master 2

DMM Belay Master 2
Top Pick Award

(25% off)
at Backcountry
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Gate keeper helps prevent crossloading
Smooth screwing action
Ensures screwgate is locked
Can be awkward to use
Small gate opening

The Top Pick for Belay Carabiner goes to the DMM Belay Master 2, a locking specific carabiner specifically designed to be used while belaying off the belay loop with a variety of devices. It is not an inexpensive choice but is the best locker we used that prevents cross-loading from occurring.

Read review: DMM Belay Master 2

Amazing Value and Lightweight

Mad Rock Super Tech Keylock Screw

Mad Rock Super Tech Keylock Screw
Best Buy Award

at Amazon
See It

Easy to grip
Not the best gate clearance
Small gate opening

No other carabiner offers as much value in a lightweight package. It's just as light and almost as high scoring as the Edelrid Pure Screw but is $3 less expensive. This is not the best belay biner and won't hold many ropes like a larger biner will. However, more most other locking biner applications, it works well at a fraction of the weight and cost. We put 2-4 on our trad climbing rack and 4-8 on our big wall climbing rack.

Read review: Mad Rock Super Tech Keylock Screw

Analysis and Test Results

Locking carabiners, or simply lockers, are just metal snap-links that are kept securely shut by way of a locking gate. While this seems simple enough, there are many styles of lockers out on the market now, designed with different tasks in mind. While there used to be very few styles of locking type carabiners beside the big and bulky, classic HMS shape, now there are so many to choose from that we have updated this review to feature some of the newest designs alongside some of our trusty lockers that have long been on our harness. Since there are as many applications for lockers as there are products on the market, let's take a look at what makes some of these carabiners in our review stand out from the crowd.

Hmm  I wonder what kind of locker I'll need up there!
Hmm, I wonder what kind of locker I'll need up there!


Our group of lockers ranged in price from $8 to $30. That's a factor of greater than 3 within the same product category. Often you'll pay significantly more for a specialized locking mechanism, belay loop keeper, or more space in the basket. Depending on your intended use, these may be worth the price. Whether or not you'll be purchasing multiples is another point to consider. A reliable and easy to use piece that lives on your belay loop may be easier to put more money down for than the few extra biners you need to beef up your rack. For something that does pretty much everything well, we like the Petzl Attache. If you're belaying on a budget, check out the Black Diamond Rocklock Screwgate, or the Mad Rock Super Tech Keylock Screw for non-belay jobs.

Carabiner Shape

The shape of the carabiner is important to its function in a given application. Some can be used interchangeably with little negative effect, and others perform poorly at tasks they are not designed for.

Diagram showing the various named parts of a locking carabiner
Diagram showing the various named parts of a locking carabiner

Offset-D Shape

The most popular style on the market, this shape comprises about 60 percent of the available carabiners produced. The Black Diamond Positron is a good small-medium sized offset-D. It is a slight modification to the standard D-shaped locker described below, with some notable improvements that make it so useful to climbers. The Offset D features a wider basket that improves function, allows for a wider gate opening and can be scaled down resulting in smaller and lighter weight lockers. Some strength is lost from the D shape, since the load is not as evenly distributed to the spine.

HMS Style

HMS, or pear-shaped lockers, have a wide basket and a narrow crotch. The Mad Rock Ultra Tech HMS is a good example of this shape. HMS stands for halb mastwurf sicherung, or the half clove hitch belay. Most climbers know this as a Munter hitch. The Munter is a hitch that takes up a lot of space on the basket or the carabiner and needs to freely move without being pinched by the spine, hence the wide basket. These are also used frequently as belay and rappel carabiners as they allow for even feeding of brake strands without pinching because of the wide, symmetrical basket used.

Carabiner shapes. L to R  Offset D  HMS  D.
Carabiner shapes. L to R, Offset D, HMS, D.

D Shaped

D-shaped lockers are not as popular but are still produced by climbing companies. The Omega Pacific ISO Locking Standard D is still seen on enough climber's racks that we included it in the review. The standard D shape is popular for those seeking high strength carabiners for use in anchoring systems since the shape keeps the load oriented along the strongest axis (the spine), but is a poor performer at many other common climbing tasks due to the tight basket and crotch shape. Other designs have improved on the D shape, such as the Petzl Am'd, which although not a true symmetrical D, keeps high major axis strength while allowing a wider gate opening and larger basket area.

Oval Shaped

The oval is the original carabiner design, and the oval shaped locker is still produced by some companies. While there are certain benefits to the oval shape, like being able to fit a lot of gear onto it, the shape is inherently weaker than others since the load is not directly in line with the spine, and does not have as wide as an opening or useful basket as Offset D or HMS lockers. We did not test any true oval locking style carabiner shapes.

Gate Closure Style

Three closure styles reviewed  magnet  twist and screw locks.
Three closure styles reviewed, magnet, twist and screw locks.

Locking type carabiners are often described as being double-action or triple-action. This basically means that to open a triple-action locker, you need to perform three separate movements. A non-locker is a single action, a regular screw gate is a double action, and a gate that requires you to twist, slide, and then open the gate would be a triple action locker. Here we describe the three styles featured in our review, which does not represent ALL styles of locking carabiner closures out there.

Screw Gate

This is by far the most popular style of gate closure system. The screw gate relies on a small metal cylinder which screws up and over the nose of the carabiner, preventing the gate from being opened. Some designs, like the DMM Master 2, use an additional closure that further prevents the screw gate from opening. The downside to standard screw gates is that they must be manually closed each time, something climbers often are forgetful about. For this reason, Petzl among others put a red stripe along the gate of the carabiner to indicate whether it is closed or not — "See red, you might be dead!"

Twist Gate

Twist gates, such as on the Petzl Am'd Twist, can sometimes be more cumbersome to open, but the locking mechanism is automatic once released, thanks to an internal spring, making for a potentially more user-friendly tool, especially when used with belaying. Just like with screw gates, grit and grime can clog up the mechanism, so they are not completely foolproof.

Magnet Gate

Okay, let's be honest, this category didn't even exist until a couple of years ago. When Black Diamond came out with the Magnetron line of locking type carabiners, some were skeptical, but they have proved worthy in many applications. They are in reality a double-action locker, even though the user must depress both sides of the magnet closures at the same time to open the gate. It is an automatically locking closure, but the magnets do attract ferrous material if left in the dirt and can become sticky or clogged. Also, when used in cold and icy conditions the gate is more likely to freeze shut than others.

Criteria for Evaluation

High on El Cap  a good example of where you might want to have the appropriate locking carabiner for the task at hand.
High on El Cap, a good example of where you might want to have the appropriate locking carabiner for the task at hand.


A locking specific carabiner should be used whenever it is the critical link in the safety system. This could be when used for belaying or rappelling, attaching to an anchor, connecting yourself to ascending devices, or during many of the other times when climbers find themselves needing to rely heavily on a single piece of equipment. While all contenders will be able to perform these tasks, some are only suited to narrow, specific situations. The Petzl Attache was the highest scoring locker for function, for its overall usefulness, but carabiners like the Omega Pacific ISO Standard Locking D scored poorly in this category for their narrow range of function.

We gave higher marks to those lockers that could function well across many applications. A small, extremely lightweight locker like the Edelrid Pure Screw is a boon to those seeking weight savings on demanding climbs or on long backcountry trips, but will not offer the same across-the-board performance as an all-purpose locker like the Mad Rock Ultra-Tech HMS. Some lockers, such as the DMM Belay Master 2, are so obviously designed for a specific purpose, such as attaching a belay device to a climbing harness belay loop, that we did not deduct any scoring for functioning poorly during uses for which they were not intended.

There are many variables that can affect a locking carabiner's function, including stock shape (round, oval or I-beam construction), gate opening style, and carabiner shape as discussed above, to name a few. Durability is included in our function score, and how well a carabiner stands up to the abuse that climbing environments can inflict on gear is an important consideration. Lightweight construction is a benefit in areas where the rope can stay clean from dirt and grit, but in places like the desert, your ultra-light belay locker might be heavily grooved after only a handful of pitches!

Neat and tidy at the belay with varied carabiner styles all functioning well in their intended roles
Neat and tidy at the belay with varied carabiner styles all functioning well in their intended roles


There has been quite the revolution in carabiner technology in the past couple of decades, and the modern climber no longer has to be content with heavy, full-sized carabiners comprising their rack. Quickdraws, racking carabiners and cams have all been re-engineered to maintain the same strength we expect from our equipment, at a fraction of the weight. Our Best Carabiner Review highlights many modern carabiner designs that can take pounds off of your harness, and while the majority of the carabiners we carry are non-lockers, if you are carrying six to eight lockers on a standard multi-pitch rock climb, the bulk and weight of those lockers can begin to add up.

The Edelrid Pure Screw was the only locker to receive a score of 10 in this category, for its scant 43 gram weight. We were also quite impressed at the Black Diamond Vaporlock Magnetron, an auto-locking carabiner that is full sized but still only 56 grams. Our Best Bang for Buck locker, the Black Diamond Rocklock Screwgate is sure nice to work with, but at 85 grams was far too heavy to carry on long routes or in large quantities.

A locker's size is an important point-were able to carry more lockers and avoid running out when building critical safety systems when they are smaller and less cumbersome. Compactness is not always favorable though, as the locker's functionality decreases the smaller the carabiner gets. One could use the smallest locker on the market to attach an auto-blocking belay device such as the Petzl Reverso to an anchor, but that carabiner would perform poorly if tasked with clipping into a bulky master point.

Weight is also one of the major deciding points in purchasing a locking type carabiners. The metal we take with us up on the cliffs and into the mountains can be a heavy burden both on the approaches as well as the climbs. By lightening our racks without leaving anything important behind, we can climb faster and have more fun, but weight savings also come at a cost. In exchange for featherweight gear, we trade in durability, price, and sometimes function. The lighter weight, I-beam carabiner construction used on lockers such as the Petzl Attache can experience gate shutter when they are knocked against another hard surface, a phenomenon that can open the screw gate if the carabiner is not oriented correctly.

Being able to pop knots and hitches into a locker quickly is an important consideration for alpine transitions.
Being able to pop knots and hitches into a locker quickly is an important consideration for alpine transitions.

Ease of Locking/Unlocking

Above we described a few of the different styles of gate closures found on the lockers that are featured in this review. What we look for in a locker is the ability to manipulate the locking mechanism with one hand, since we are often performing our tasks at the anchor with our other hand holding onto either the rock or the anchor, ability to open and close the carabiner while wearing gloves, and the overall ease of use.

Most of the screw gates performed about the same in our review tests; however, some, like the Omega Pacific ISO Standard Locking D, we found too easy to over-tighten both in the open and closed position. When screw gates rattle a little bit on the gate, having perhaps been milled too large, they can end up screwing onto the stopper ring at the bottom of the threads, making them stick.

The only twist lock carabiner in the review, the Petzl Am'd, was a welcome relief to the clunky and difficult-to-open twist locks and triple-action lockers that Petzl has produced before, and was easily operated one-handedly. We preferred the twist lock style to the Magnetron style auto-locker for a couple of reasons. A common scenario for needing to unlock and remove a carabiner is at an anchor, where multiple lockers might be attached to a master point and are under load. In these situations, the unique Black Diamond Vaporlock Magnetron felt more difficult to remove than others because of the need to depress both sides equally at the same time.

When climbing ice routes  it helps to make sure that your lockers are easily opened and closed with gloved hands.
When climbing ice routes, it helps to make sure that your lockers are easily opened and closed with gloved hands.

Gate Hang up

When using locking carabiners with thin slings and cord, racking them onto your harness' gear loops, and especially when clipping them to bolt hangers, having a snag-free nose on your carabiners is the way to go. In virtually no scenario that we could think up would a standard notched carabiner nose be superior. Key lock carabiners are no longer a new feat of engineering that is only being put onto a handful of models; these days almost any locking carabiner is available in a key lock version, with little if any price difference, so there is no reason to not give yourself the smoothest interaction possible between your lockers and whatever you have to clip them too.

The best of these keylock style noses is found on the Petzl Attache -there is no abrupt change in stock thickness, giving a nice smooth taper. Other keyed noses like the Mad Rock Ultra HMS were thicker and did not clip as easily. Our least favorite carabiner in this category was the Omega Pacific ISO Standard Locking D, a design that still uses the traditional notched nose and which hangs up on everything.

When multi-pitch climbing on bolted anchors  having a combo of compact lockers and large HMS carabiners is a good idea  and it makes it easier when they are keylock so they won't snag on hangers or on weighted anchors.
When multi-pitch climbing on bolted anchors, having a combo of compact lockers and large HMS carabiners is a good idea, and it makes it easier when they are keylock so they won't snag on hangers or on weighted anchors.

Gate Clearance

The size and shape of a carabiner has a direct effect on the distance that its gate is going to be able to open. D-shaped lockers have some of the smallest gate openings because of the symmetrical design, with HMS and Offset D shapes usually providing the largest clearance, thanks to their asymmetrical shape. Shape does what it can, of course, but when an Offset D shape is miniaturized, as in the case of the Black Diamond Positron, there will be a negative effect on its gate clearance. If you need wider gate clearance, the Mad Rock Ultra HMS was the second best in this category with a gate clearance of a whopping 2.3 cm and is only sightly larger than the Positron. The best performer was the Petal Attache, opening up 2.4 cm, almost a full centimeter wider than the Omega Pacific Standard Locking D.

Why does gate clearance matter? If you are only using your locking carabiners for belay duty, and are clipping a maximum of one or two strands for belaying or rappelling, then clearance is not a big issue. But if you find yourself at a gear anchor, with a fat master point comprised of several loops of thick 7mm cord that you need to clip into, you would prefer a carabiner like the Black Diamond Rocklock Screwgate with the larger gate opening over the mini version that barely clips into a bolt hanger.

What is going on?! Locking carabiners here are used to clove hitch climbers on an alpine face and for belaying a third climber with an ATC Guide. Large gate opening allows us to easily stack things into master point lockers.
What is going on?! Locking carabiners here are used to clove hitch climbers on an alpine face and for belaying a third climber with an ATC Guide. Large gate opening allows us to easily stack things into master point lockers.


Our fleet of locking carabiners ready to be reviewed!
Our fleet of locking carabiners ready to be reviewed!

We chose 10 lockers for our review, in an effort to discover what models performed the best for climbing and adventuring. Since these locking carabiners are designed intentionally to be used in technical climbing systems, some performed much better than other in specific tasks. Even within this category, there were several different styles of carabiner represented, each with their own merits. While your needs will dictate the type of carabiner you should be shopping for, there were clearly ones that rose to the top in our tests and which should find their way onto your climbing harness. Because most climbing situations require multiple locking carabiners, read the complete review, as well as the buying advice to find out what locker worked best for what type of use. You will find that purchasing a variety of the different lockers highlighted in this review to suit your needs will lead to better performance at the crag or in the mountains.

Ryan Huetter