Trap doors of non-metallic materials; non-metallic transportable buildings in the nature of inspection chambers; non-metallic doors for use as inspection covers; non-metallic doors for use as access chamber covers; suspended ceilings made of non-metallic materials comprising panels; boards of gypsum plaster; structural frameworks made of non-metallic materials for buildings; building elements made of non-metallic materials, namely, wall claddings, pillars, soffits; manufactured building eleme...