The beds of pickup trucks and similar vehicles are normally finished in the same manner as the outside of the vehicles; that is, the same type of sheet metal and paint finish are used therefor, presenting a uniform appearance when the vehicle is new. Such vehicles, however, are often subjected to severe duty, such as the transporting of construction materials, tools, firewood, and like materials which are likely to scrape, scratch, and otherwise mar the finish of the inside of the truck bed. Eventually, from the combined effects of abrasive use, weathering, and other deleterious conditions, the truck bed loses its like-new appearance. In vehicles used exclusively for heavy industrial or agricultural purposes, the condition of the truck bed may not be a great concern, but for more general purposes, the condition of the truck bed is as important as the condition of the rest of the vehicle. As the finish of the truck bed becomes marred by the scraping or scratching of the paint, rust quickly develops on the unprotected sheet metal. Where severe, the rust will eventually destroy the bed and will, at the least, make the bed generally unsuitable for light duty uses, such as the transporting of passengers or grocery bags, and greatly reduce the resale value of the vehicle.
Many manufacturers, therefore, now provide truck bed liners to protect the finish of the bed from damage caused by abrasive cargoes. The liners generally conform to the shape of the bed and provide the requisite protective covering to maintain its condition. When necessary for resale or other purposes, the liners can normally be removed, thereby exposing the bed with the original finish unmarred by previously transported cargo. The liners, in conforming to the shape of the truck bed, generally cover the bottom and sides of the bed and have flanges which extend outwardly from the sides of the liner to cover the upper edges of the sides of the truck bed. Holes are then normally drilled through the flanges and the upper edges of the sides of the truck bed for receiving screws which secure the liner thereto.
The above procedure has certain definite disadvantages. Drilling holes in the truck body provides additional sites from which rust may develop as the protective paint covering is removed or chipped away by the drilling. Since the liners are normally of a plastic material, and are exposed outdoors a great deal of the time, the liners are subject to expansion and contraction from temperature extremes, and at a different rate from that of the metal used for the truck body. Thus, the liners may buckle, warp, pull loose, or crack, due to the nonuniform expansion and contraction of the truck body and the liner, reducing their attractiveness and effectiveness. In addition, the movement of the unsecured portions of the liner relative to the rigidly secured flanges often leads to cracking of the liner around the screws and eventually requires replacement of the liner. If the truck is to be resold and the liner is removed, the truck bed will normally be in good condition, but the drilled holes remain, providing rust-formation sites and an unsightly appearance.
Another type of liner securing means which has been used commercially consists of expansion anchoring bolts extending through the outwardly extending flanges into the stake pockets of the bed side walls. This type of securing means also has many of the same disadvantages as the previously described screws in the flanges, particularly with respect to the nonuniform expansion of the bed liner in response to changes in temperature.