One of the surprises you don't want to get out on the road is to realize that there are items on your RV or trailer that are lower than your bumper...such as the valves on your dump. When backing up your vehicle be sure to watch for railroad ties or other blocks that are often designed to set off an RV site. It's very easy to hit one of your dump valves and just the slightest bend in that valve can render them unusable. Look below your RV, especially when you're backing up.