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Black Diamond GridLock Magnetron Review

A secure auto-locking and anti-crossloading locker designed for belaying that is simply more annoying to use than the other alternatives
Black Diamond GridLock Magnetron
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Price:  $40 List
Pros:  Magnetron technology is securely auto-locking, prevents cross-loading while belaying
Cons:  Very fiddly and time consuming, hard to use with gloves, heavy, instructions for use with active assist braking devices not intuitive
Manufacturer:   Black Diamond Equipment
By Andy Wellman ⋅ Senior Review Editor  ⋅  Aug 15, 2019
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  • Overall Utility - 25% 4.0
  • Ease of Unlocking and Locking - 25% 5.0
  • Compactness and Weight - 20% 4.0
  • Gate Security - 20% 9.0
  • Gate Clearance - 10% 9.0

Our Verdict

The Black Diamond GridLock Magnetron is a belay specific locker that uses magnetic technology in the gate to create an auto-locking system that is quite a bit different than most standard twist locks. In order to open the gate, you must squeeze two lever arms, one on each side of the gate, which releases the magnetic grip with the nose. The gate also features a curved extension bar off the bottom that combines with a unique shape to trap the belay loop of the harness in place, preventing potential cross-loading. While this carabiner is effective for the purpose it is designed for, we found it to be laborious to use, and honestly felt a bit exasperated having to open and close the gate so many times to fiddle the locker onto our belay loop, or to add the belay device, especially during long sport climbing sessions or at the gym. This is one case where the convenience of a screw gate, which doesn't automatically lock whenever it's shut, may be worth the trade-offs, and BD does make the GridLock Screwgate for those interested.

Our Analysis and Test Results

While the GridLock Magnetron is one of the most popular belay lockers that we see at the crags and in the gym, our testing reveals that it is laborious to use and indeed is often used incorrectly, which we are even guilty of before being clued in by in-depth internet research. The internal bar attached to the gate requires the gate to be opened in order to slide the belay loop into the correct position in the crotch of the locker, if you are belaying with an ATC. However, if you are belaying with a GriGri or other similar device, you are supposed to load it into the small end, trapped by the internal bar, with the large end attached to your belay loop. Not only is this annoying and difficult to do, but is completely counter-intuitive, to the point where we have never actually seen someone using this locker correctly in this way at the crag. Not convinced, check out the screenshot below of Black Diamond's visual instructions for this locker, taken directly from their website.

This is a screenshot of diagrams taken directly off of BD's...
This is a screenshot of diagrams taken directly off of BD's instructions on their website. It clearly shows that you should flip the locker around to belay with a GriGri, and that belaying the way we see everyone doing it offers no added anti-crossloading benefit compared to a normal locker.

In the case of the GridLock, we actually think the magnets are partly responsible for the constant difficulty in using this locker, and would instead recommend the Black Diamond GridLock Screwgate, which won't be quite as secure with the gate closure, but will be far easier to use. Regardless, we would highly recommend checking out other belay specific carabiners before buying this one.

Performance Comparison

Making one of about eight rappels off the summit of South Howser...
Making one of about eight rappels off the summit of South Howser Tower in the Bugaboos after climbing the Beckey-Chouinard, using the Gridlock Magnetron as a rappel locker. While anti-crossloading features are more important for belaying and tying in short than for rappelling, the thick round stock in the basket means that it works well for this purpose also.

Overall Utility

In terms of overall utility, we find this locker to be one of the lowest scorers, and were the most frequently frustrated while using it, a poor attribute of any product no matter what its purpose. Since the interior lever bar is attached directly to the gate, in order to move it, one must also open the gate. This requires a minimum of two gate openings any time one wants to either put someone on belay or take them off belay, which simply shouldn't be necessary. This action is compounded by the fact that the Magnetron gate auto-locks every time it snaps closed, requiring you to squeeze the triggers to open it every time. The fact that there is a different method of loading a GriGri or other similar device compared to an ATC, and that it is counter-intuitive, is another knock against the design. The internal bar also prevents this locker from being a good choice for other applications, such as building multi-pitch anchors, and the magnetron technology is hard to manipulate with gloves on in the winter. All of these facts contribute to it being one of the least versatile lockers that we tested, and receiving a correspondingly low score.

According to Black Diamond's instructions, this is the correct way...
According to Black Diamond's instructions, this is the correct way to use this locker when belaying with a GriGri or other similar device. To get the device and locker into this position is even more laborious than to orient it the other way, and indeed, we cannot recall ever having seen someone belaying in this manner, suggesting that the usage is very non-inuitive.

Check out in this photo how the gate must be opened in order for the...
Check out in this photo how the gate must be opened in order for the attached lever arm to open enough to allow the belay loop to move into the correct position inside the small end of the locker. This design requires lots of movements and actions compared to competing anti-crossloading options, and when combined with the magnetron gate, becomes fairly annoying to repeat all the time.

Ease of Unlocking and Locking

To lock this carabiner is as simple as can be, the magnetic technology automatically causes it to lock the moment the gate snaps closed. To unlock it requires pinching the two metal levers on each side of the gate, which can be hard with gloves on. While this technology works well with a simple pear shaped locker, it actually makes this locker more difficult to manage, because of the aforementioned lever arm making it difficult to open the gate at times. A low scorer in this department.

In order to unlock the gate of this 'biner, one must squeeze the...
In order to unlock the gate of this 'biner, one must squeeze the bottoms of both of these lever arms, one on each side of the gate. This releases their grip with magnets in the nose, allowing the gate to open. It snaps closed and locks automatically of its own accord.

Compactness and Weight

We weighed this locker at 82g on our independent scale, which ranks it up there near the top in terms of heaviest carabiners. Combined with its heavy weight is the shape of the design, which is slightly figure-eight shaped with one end larger and one end smaller. This makes it bigger and less compact than other lockers. These two factors once again make it a low scorer for this metric.

At 82g, this is one of the heaviest lockers in our review, ensuring...
At 82g, this is one of the heaviest lockers in our review, ensuring that we wouldn't be too excited to haul it up many long routes in the mountains. It is best used exclusively for belaying at the crag or gym.

Gate Security

The Magnetron gate greatly adds to the security of this locking carabiner, which is the main reason people would be inclined to buy it. When the spring-loaded gate snaps closed, it automatically locks, and the fact that to unlock it requires pinching a specific place on both sides of the gate makes it extremely unlikely that it would accidentally open on its own. While we think the GridLock Screwgate would be a much easier version of this locker to use, we concede that the Magnetron is more secure. The only thing you should watch for is that ice or ferrous dirt can clog the magnets, thereby inhibiting the ability for it to lock closed, so a visual inspection now and again is still a good idea.

Due to the odd, figure-eight like shape of this locker, we found...
Due to the odd, figure-eight like shape of this locker, we found that it sits a bit odd on the harness gear loop, and because it is auto-locking, also requires a bit of fiddling to remove from the gear loops as well.

Gate Clearance

We measured the gate clearance of this locker at 2.4 cm, making it among the largest that we tested. This is great for getting belay devices or knots on or off the nose of the carabiner, but this also comes with a catch. The clearance of the internal bar is much smaller. Since it is attached to the gate, it can easily inhibit the gate from opening if a belay loop or GriGri isn't positioned correctly within its small ring.

We measuured the amount of gate clearance at 2.4 cm, as you can see...
We measuured the amount of gate clearance at 2.4 cm, as you can see here. This is quite large for a locker, making it relatively easy to get devices on and off of the basket.


One of the more expensive lockers in this review, it costs more than double the price of numerous other lockers that are easy to belay with. Much of the price is due to the Magnetron technology — the Screwgate version is much cheaper, nearly half the price, making it a far better value. Since we don't think it performs well compared to the competition and isn't super cheap, we can't call the GridLock a great value.

While it can be used for other uses besides belaying off the...
While it can be used for other uses besides belaying off the harness, as shown here, it is once again more difficult to set up. First one opens the gate to clip it to the red sling at the top of the photo. Then one must flip it upside down, and open the gate again to squeeze the sling into the top loop of the 'biner. Then one must open the gate again to put the belay device into position. To us, it just feels like more labor than other lockers, and more than should be necessary.


The Black Diamond GridLock Magnetron is a belay specific carabiner designed to prevent the possibility of cross-loading when catching a fall. We have seen many wildly different designs that attempt to solve this problem, but unfortunately Black Diamond's is the most annoying to use. Manipulating the belay carabiner repeatedly is an inherent part of belaying while climbing, and since this design makes this a challenging task compared to others, it is not by any means the first one that we would recommend buying.

When guiding, traveling on a glacier, climbing in a party of three...
When guiding, traveling on a glacier, climbing in a party of three on one rope, or simul-climbing, as we are here, it is common to tie into the rope short using a locking carabiner. This is one situation where you definitely want one that automatically prevents crossloading, because the chances of suddenly weighting the rope and 'biner are high. The Gridlock Magnetron is the perfect choice in this situation.

Andy Wellman
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