Abstract: A light weight convertible cover assembly for use on flat bed trucks, trailers and the like which enables the platforms to be used without any impediments to vertical loading during favorable weather and yet provides means for a rapid and easy protection from the weather in the event of inclemency. The cover assembly includes a stanchion or upright mounted at each corner of the load supporting platform. Opposing uprights at each end of the platform are interconnected by rigid horizontal members and the uprights diverge toward the top along the sides of the platform. Removable supporting cables interconnecting opposing uprights and extending along the sides of the platform support the flexible protective cover. A central support cable secured to the rigid horizontal member is provided parallel to the corner cables such that when the cover is extended over the load it has a three line stable support preventing sag or the like.