i used a car dolly today from uhaul and liked how the ramps slid out but had a cathc keeping them from slidin all the way out and used a spring loaded pin to lock them in the stored possition. they rattle like nobodies business though giong down the road.
buddy has a friend that built his own flat bed and used the ramps as the side of the bed, he used some anlge at the top of the ramp and maybe some angle or small tube at the tail end of the bed to keep the ramps from falling off. then they had the typical 4 inch piece for the stake pockets. worked good as well. just some ideas