Using the trailer fenders as steps to climb on and off of a boat is a common practice, but the top of the fender can become slick, especially right after you retrieve the boat or during washing. More than once my foot has slipped off my boat's trailer fender. Thankfully, I have not been injured as a result, and to continue that good fortune, I added 4-inch strips of 3M Safety-Walk slip-resistant adhesive tape to the tops of the fenders. The grit is aggressive and offers grip even when wet or covered with soap suds. Make sure you clean the fender tops well before applying the tape, which sells for about $22 for a 15-foot roll.