4531 Steel windows, doors and frames (sets) (21) Steel windows, doors and frames, installed in external faces of buildings 4532 Steel screens and shutters (4) Steel screens and associated frames for decorative purposes or security and light control; screens with infill of louvres, mesh, bars, etc., to prevent the ingress of people, rain, animals and objects 4534 Steel roof and ceiling windows and lights (0) Steel lights fixed into roofing and ceilings