Vehicle Parts, Auto Accessories and Care Products Design Car Box Service in The Trunk by Andrew Chu Car Box is a foldable storage box designed for the trunk of a car. The trapezoidal shape follows the angle of about 80 degrees of the rear seats, so the box fits the trunk and uses space that is often left empty. A flip-down lid is held by a strong magnet, which lets rear seat occupants reach stored items while driving. The body is made of expanded polypropylene, a light foamed plastic that resists impact and can be recycled. Folding clasps on each side allow assembly or folding within five seconds without tools.