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Date of Incident









No injury


The incident: - a top-roping climber took a fall on a GridLock carabiner with the gate lodged in the open position.
The risk: - the rope could have come out of the open gate, and the climber could have had
an uncontrolled fall to the floor.
The outcome: - the rope stayed in the carabiner and the belay device worked as intended to
catch the fall. No-one was hurt and the climber was unaware of the near miss at the time.

We were running a family have-a-go climbing session on a ~10m outdoor artificial climbing wall, with under-18's belaying on ATCs, each supervised by an adult who held a permit issued by the national youth organisation which we are members of. This was the climbing team's first time at this wall, and first time belaying off slings attached to ground anchors, rather than directly off the belayer's harness. The belay setup was in accordance with written operating procedures for the wall.

During the course of the afternoon, the belayers DMM Gridlock carabiner became rotated 180 degrees. While it was not unsafe in that position, the adult on that rope system let
the under -18 belayer know that they could flip it back if they wished to. While doing so, the Scout undid and rotated the carabiner, but did not fully re-seat the sling into the small end of the Gridlock carabiner. In addition the gate was closed but the screwgate was not done up.

The DMM Gridlock has an unique shape, designed as an additional safety feature over a
plain HMS-shape carabiner. In this case, the unusual shape meant that once the rope was put under tension, the unseated sling pulled the gate of the carabiner into a fully open position. This was not noticed, was climbed on and a fall was taken (and thankfully held) on it.


When climbing at our 'home' wall, we belay off the belayers harness, using ballast bags as required. As the person belaying changes often in this situation we operate a system of pre-climb 2-way buddy checks before every climb, which includes the climber and belayer both checking each other's carabiners, knots and harnesses.

At this site, the rope and ATC belay device was clipped via a sling to the floor, not to an
individual belayer. This meant that the belay device carabiner should not have been touched
or adjusted between climbers. For that reason we did not insist upon the 2-way buddy
checks we use at our home wall, and instead focussed on a 1-way check only, from climber
to belayer. We assigned dedicated under-18s to assist with this specific task, to support the belayers.
The adult supervisor watched the climbers safety checks and monitored the belayer’s hands on the rope while belaying, however, they did not think to recheck the belay system itself and did not see that the carabiner gate was now fully open. When the climber fell and was, thankfully, properly stopped by the belay system, the problem was seen, immediately rectified, and the climb was continued without further incident.

Action taken:
Following this incident we have replaced all the Gridlock Carabiners, and have documented and implemented a more robust and performative 2-way buddy check before each and every climb, regardless of location or the type of anchor setup.




Reported By


Wearing Helmets?

Rescue Services Involved?



5 October 2022 at 20:50:36

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