In reply to Ron Rees Davies:
> the ''self locking" thing is a bit of a gimmick when you still have to hold the dead end, but otherwise it's a good belay
Just like any other belay device, where you should keep hold of the dead end if you've got someone on the live end.
The facility makes it easier to hold a climber resting on a route, again the same as more technical assisted braking devices.