I have a roof rack and I use it all the time. They go on easy and come off easy. The ones that clamp onto the gutter DO NOT OVER TITEN them they will bend the gutter. Also before you put it on check you gutters for rust if you have some clean it up first. Also at less ones a year take it off and clean the gutters and check them because with the clamps the are blocking the gutters and dirt and water will set in it and start rusting. I have placed a board on top and 3 people stood on top as spotters and they were NOT little a total around 750 to 800 lb. and it held up.