Abstract: A unitary liner for truck beds including a flange for positioning the side wall of the liner relative to the side wall of the truck such that the bottom of the liner side wall and adjacent portions of the bottom side walls are displaced from the bed bottom wall. The bottom wall of the liner includes raised ribbed portion displaced from the side and front walls to create peripheral drains and the bottom wall is inclined relative to the side, front and bottom walls of the liner at the corners of the side and front walls to prevent water and other foreign material from collecting at the corners. A mounting device is provided which is secured to the side rail of the bed through a slot provided in the side wall of the liner to permit horizontal and vertically downward movement of the liner and prevent vertically upward movement of the liner.