We have them. The only problem with our trailer is that the tires as close together, not leaving a lot of room between them for these things. We have to force them in. Our daughter has a Sunset Trail fifth wheel and the wheels are further apart. It is easy to back right over them if the difference side to side is too great. In that case you would want to use a board as well.
2012 Cruiser Sahara 330SS
2015 F250 Super Duty diesel