Another common off-roading accessory, "rock rails" or "rock sliders", are heavy metal rails or tubes which runs alongside the rocker panels and serves to protect the sides of the vehicle that are exposed on particularly rough terrain, or where there is a risk that lower edges of the vehicle between the wheels might come into contact with rocks below. This strategy can be extended to the entire vehicle, in which case it is referred to as an "external cage" or "exocage". External cages help protect the entire body of the vehicle in the case of a rollover or slide into an obstacle.