Protection for the rear carpet areas of an automobile such as a sport utility vehicle is provided by a unitary sheet of heavy-gauge extruded, high-density polyethylene. The floor liner has a floor panel which covers the floor of the cargo area of a sports utility vehicle. The floor panel has sides which extend along and are tucked under the wheel well trim panels on either side of the cargo area. Integrally formed with, and attached to, the forward edge of the floor panel, are two cargo extension panels. The cargo extension panels form a continuation of the forward edge of the cargo floor panel and are separated from each other by a seat back accommodation slot. This slot divides the cargo extension panels so that each panel corresponds to the width of the seat back positioned forward of each panel. Continuing on from the cargo extension panels are recumbent panels which are integrally formed with and joined to the cargo panels. These in turn are joined to integrally formed seat back panels. The joints between the panels are of the type known as a "living hinge" and are cold-formed into the material of the liner itself. The double living hinges provide resilient, long-life hinges impervious to liquids and provide flat extended edges of improved appearance and safety. The spring-loaded extension panel of a vehicle urges the seat back panel against a seat back and hence retains the liner without additional fasteners.