Abstract: An improved hollow beam suitable for construction of screened enclosures and the like, the beam being composed of a mated pair of generally C-shaped extruded members, preferably of identical configuration. Each extruded member comprises a side wall, a male flange member forming one of the short arms of the C-shape, and a female flange member forming the other of the short arms of the C-shape. The combination of the male and female flanges define a coupling assembly presenting a generally planar mated exterior surface on the end walls.