How do you work them?? What keeps them from starting to go down before your ready?? What I'm wanting to do is get one long enough for my little 22 ft long grader. I need to back on as most weight on rear of grader. Will it start down before front wheels get on? Or do I need to release a control--which might be hard right now as my park brake might not hold machine on much of a slope--need to fix. LB