Abstract: An enclosure structure suitable for use in constructing fixed enclosures, trailers, travel trailers, motor homes, buses, and mobile homes, comprising a plurality of wall panels, top panels, and bottom panels, at least one of the panels having a structural frame formed of elongate frame members welded together, each frame member having a tubular member and a channel-forming member of L-shaped cross-section affixed at one edge to the tubular member and cooperating therewith to define a channel, the frame having an insulating material such as a foam plastic arranged intermediate the frame members and outer walls formed of plywood and sheet metal or panels formed of fiberglass and resin. Adjacent panels disposed substantially at right angles to the channel-containing panel have their edges disposed within the channels and means such as screws affixing the channels to the engaged panels.