bedliner

noun

1. A plastic shell that lines the bed of a vehicle.

   “Pickup truck bedliners are durable high-density molded polyethylene inserts that slip over the exposed cargo bed.”

   “Even when you order your late - model pickup with a drop-in plastic bedliner from the factory, you might experience rust buildup between the plastic bedliner and the sheet metal of the truck bed after a few years.”