Abstract: Systems and methods related to cargo enclosures feature side frame assemblies securable to a pickup truck cargo box or similar structure. The frame assemblies include longitudinal channels that are movable from a closed position to an extended position by an actuator mechanism. The actuator mechanism includes oppositely disposed linear actuators anchored to one of the channels, forcing hinged rails from an overlapping relationship to a coaxial relationship. The frame assembly may include a cross- or scissor-brace to improve stability. A pliable fabric forms at least one and up to three panel sidewalls that extend and retract simultaneously with the movement of the channels. A top cover is selectively securable to the frame assemblies.