FURNISHING AND/OR INSTALLING, BY CONTRACT SERVICE OF PREFABRICATED AND PARTIALLY PREFABRICATED DOORS, WINDOWS, ELEVATOR DOORS AND CABS, FOLDING PARTITIONS, [ CUSTOM CONVECTOR ENCLOSURES, ARCHITECTURAL PORCELAIN AND PANELS, ACCOUSTICAL ENVIRONMENTAL ROOMS, NAIL HANDLING EQUIPMENT, REMOTE CONTROLS FOR WINDOWS ] AND LIKE BUILDING PRODUCTS TO BUILDING CONTRACTORS AND ULTIMATE USERS