Disclosed is a one piece self sustaining fastener for securing a protective liner to the bed of a pick-up truck, the liner having on its two opposite vertical sides openings for receiving individual fasteners, each fastener having an extending portion adapted to pass into an opening of the liner and pass around and out of contact with an adjacent horizontal projecting portion of the rail of the bed, the extending portion having a free end that by a flexing action engages the inside wall of the rail at a point close to but spaced from the upper inside wall of the rail, the fastener also has a base portion at the inner end of the extending portion, including a projecting surface that has a portion that exceeds the dimension of the opening and which engages the outside adjacent surface of the liner, the base portion also has a portion that acts as a pivot when inserting the fastener into the opening and an opposite portion that by thumb pressure assumes a snap locking position after which the extending portion and the base portion fasten the liner to the bed.