19 NON-METALLIC BUILDING MATERIALS, NAMELY STRUCTURAL FRAMEWORKS, FRAMES, GIRDERS, PANELS, TRUSSES, BEAMS, COLUMNS, PLATES AND FRAMEWORK CONNECTING ELEMENTS, NAMELY STRAIGHT CONNECTORS, INTERNAL AND EXTERNAL ARCH (ANGLED) CONNECTORS, TEE CONNECTORS, CROSS-JUNCTIONS, CONNECTION CHANGE KITS, BASE PLATES, EXTENSION ADAPTERS, END BLANKING PLATES, SUSPENSION BOSSES, SUSPENSION BRACKETS, DOUBLE HANGING BRACKETS AND PANEL INTERFACE BRACKETS