Aluminum tread plate (ATP) is aluminum that comes in rolls and can be used to cover the floor, walls, and outside areas of a trailer.
It normally has a diamond like pattern but patterns can differ depending on brand. It is normally glued down when applied to the inside walls or floors but attached with screws when used outside the trailer.
On the outside it is used as a stone guard around the bottom portions of the trailer where rocks and other debris might fly up and cause damage to the trailer exterior. These areas are along the bottom sides and front lower areas but it can be used most anywhere.