6 METAL CONSTRUCTION ELEMENTS FOR SPACE FRAMEWORKS, NAMELY, TUBULAR RODS, SECTIONAL RODS, CONNECTING PIECES IN THE NATURE OF BUILDINGS IN THE FORM OF ROOF STRUCTURES, INCLUDING DOMES, CEILINGS, WALLS, SHEDS, AIRPLANE HANGARS, GREENHOUSES, TOWERS INCLUDING DRILLING TOWERS AND COOLING TOWERS AS WELL AS TOWERS FOR CHEMICAL PLANTS, BRIDGES, PYLONS, ROSTRA, STANDS, SALES STANDS, WING STRUCTURES AND SIMILAR STRUCTURES FOR THEATERS, FILMS, TELEVISION, ADVERTISING, SCAFFOLDING, MAINTENANCE FRAMEWORKS FOR AIRPLANES; STRUCTURAL PANELS MADE OF METAL ALONE OR IN COMBINATION WITH OTHER MATERIALS; METAL PIPELINES AND ELEMENTS THEREOF, NAMELY, METAL PIPES, METAL PIPE FITTINGS, METAL WASHERS, METAL MOUNTINGS AND METAL GASKETS