I use large rubber chocks,I started out with the cheap plastic ones.Will never use a plastic one again.We came home from a trip one time I was tired and was unhooking the trailer, I set my plastic chocks but was lazy and did'nt load them or release the bind on the ball.When lowering the jack I saw it was stuck on the ball but kept raising the tounge up.When the trailer did release it jumped off the ball the trailer started moving backward crushed the plastic chocks and kept going for about a foot before it stopped.
I made many mistakes that day that caused that to happen,it was not just the plastic chocks that failed.
What really scared me was if the slight slope was the other way the trailer could have rolled forward trapping me between the truck and trailer.
So now I use large rubber chocks I set the rear ones back up slightly against them then set the front put the truck in neutral and let it settle,then I raise the hitch off the ball and the last thing is unhook the safety chains.
