Although my trailer does have a rear ladder, I have found
one of these to be a much safer, comfortable, and easy to use solution. I string the cover out on the ground behind the trailer and gather the sides so it is like a long large rope. I put the ladder up on the rear of my trailer, I go up carrying just the end and have my son feed the cover all up as I walk or crawl to the front of the trailer. I then just unfold the sides and let them fall down the side as I walk or crawl to the rear and then bring the rear of the cover back down as I descend. It works very well and quickly.
Another advantage to that ladder is that it is very easy to store and transport, either in the trailer of the back of my truck.
Barney