Fiberglass, hard plastic or aluminum tonneau covers are also common. Some may be painted to match the truck, are solid in construction, and can be locked. These covers are usually heavy and require gas struts to assist in opening and closing. They operate much like a vehicle's hood, typically opening from the tailgate end of the bed (back to front). Some have multiple compartments that open front to back, back to front, side to side, or even rise vertically. Fiberglass, hard plastic or aluminum tonneau covers are sometimes installed as a factory option on new vehicles.