Horizontally spaced vertical posts each include a square tubular extruded plastic sleeve enclosing a square tubular metal reinforcing post having a lower end portion with keyhole and vertical slots in each side for receiving bolts preassembled to a supporting frame or substructure. Upper and lower elongated rails each include a tubular extruded plastic body enclosing a metal reinforcing channel and also define a longitudinally extending open cavity. Opposite end portions of the rails project into corresponding openings within the posts, and an elongated extruded plastic cap has longitudinal snap clips engaging opposing lips projecting into the cavity within the upper rail. A plurality of plastic vertical spindles have upper and lower end portions projecting into the bodies and channels of the upper and lower rails, and the end portions of the rail bodies have outwardly projecting retaining barbs within the posts. Each metal reinforcing post has outwardly and downwardly projecting barbs which secure the corresponding plastic sleeve, and the downwardly facing cavity within the lower rail body is adapted to receive a lighting strip.