I have a lift that was purchased used at an auction and it does not have a load backrest. I think from what I've read that the backrest is not required when what you're lifting is not in danger of falling. Anyway my question is what stops the forks from coming off if they are moved? Is there anything specific I can look for to know the forks can't come off? And if I can't find anything then what can I do to so they won't off if anyone adjusts the width of them?