I think the stride on some dogs does not match the spacing on some stairs. Our greyhound never used the trailer steps, the distance between two steps was much smaller that the distance between his front and back legs. Some of our border collies go down our house stairs with their bodies at a 45deg angle to straight down the stairs; I think because it places their front and back legs at the spacing between the stair treds. Adding covers to trailer steps will not resolve an issue with the spacing between the steps.