Most dump beds lower by gravity with no hydraulic down pressure, so the weight of the bed, plus whatever is inside it is all the lock has to support. I can't imagine many situations where a heavily loaded bed would need to be raised for work underneath it, so the weight of the empty bed, although considerable in some cases, would be all the lock has to support. I always lowered the bed to be in contact with the lock, particularly if I had to work on any of the lift plumbing. Even with a lock in place, I did my best to avoid pinch or crush points whenever possible.
Jerry
