A sign is formed from a plurality of panels abutted edge-to-edge. A main elongate reinforcing member has a transverse head for attachment thereto of a mounting device for the sign, and a depending leg terminating in an offset foot secured to the rear of a first sign panel adjacent an abutting edge of the panel. A second, elongate, reinforcing member has a generally L-shaped cross-section including a foot portion secured to the rear of an adjacent second sign panel at the edge abutting the first panel and an upright portion abutting the leg of the main reinforcing member. One of the reinforcing members has a flange at the foot projecting into a recess in the foot portion of the other reinforcing member. The head of the reinforcing member is offset with respect to the leg on the opposite side from the projection of the foot to expose the foot for rivetting to the plate.

End plastic connectors on the ends of two construction members like concrete forms. Each connector has a pair of bosses on opposite corners and a pair of openings in opposite corners so that the bosses on one connector mate with the openings in the other connector. Each boss has an annular rib sized to press through the associated opening, which is circular with a pair of flats, to latch the connectors together. Each rib is spaced from the remainder of the associated connector a greater distance than the thickness of the material of the connectors around the openings thereby permitting limited angular adjustment in orientation between connectors. Each construction member is a piece of dimensional lumber in one form of the invention, to which the end connectors are attached by nailing. In the other form of the invention, each construction member is a plastic extrusion and the end connectors have protrusions interfitting into the plastic extrusion. The wall of the extrusion at one side is shaped into a lipped dove-tailed keyway extending from end to end of the extrusion. A locking cam secures a stake to the construction member. The clamp has a rectangular base that fits into the keyway and locks therein by turning. The plastics are formed of polyethylene, which has a release agent, and which has an ultraviolet stabilizer. Extrusions contain titanium dioxide pigmentation for maximum sun ray reflection to reduce extrusion flexibility by heating.

A common structural member for use at several locations within a truck body is comprised of an elongated member having a uniform cross-section. The common structural member has a flat surface with stiffening ribs and a first pair of mutually parallel walls along its longitudinal edges. A longitudinal T-slot extends along a first one of the parallel walls, while a longitudinal first groove extends along the second one of the walls. A longitudinal notch or second groove is situated at the second wall, and one of the notch or grooves is arranged at right angles to the T-slot while the other of the notch or grooves is arranged parallel to the T-slot. Each of the notch and grooves is adapted to accept a sheet metal panel therein. The T-slot comprises an inset channel, a slot perpendicularly intersecting said channel, and a recess opposing the slot. The T-slot further comprises at least one enlarged aperture adapted to accept a bolt or a nut therethrough for insertion into the T-slot recessed channel. In another embodiment, the common member further comprises a second pair of mutually parallel walls joined perpendicularly to the first pair of mutually parallel walls, thereby forming four longitudinal edges. Either a T-slot or a groove is situated at each of the longitudinal edges, with each of the T-slot or grooves having a particular orientation, relative to each other, such that the common member can be used at several locations throughout a truck body.