A vehicle includes a box extending from a cab and including a floor and a first sidewall attached to a headboard, via a hinge assembly, disposed normal to the floor and sidewall. The hinge assembly is configured to allow the first sidewall to rotate away from the floor at the headboard. The vehicle also includes a latch mechanism. The latch mechanism includes a pin having an end and a shaft attached to the first sidewall and a receiver having a plate hingedly connected to the receiver. Upon rotation of the first sidewall toward the floor, the end fits into the receiver and the plate locks the shaft to secure the first sidewall to the floor.