Abstract: A damper or door plate construction and mount which is adapted to in situ assembly including a core plate of sheet plastic, a thin covering of porous foam material on each side, and a mounting shaft on a pivoting axis for the damper. The mounting shaft is secured at each end within the confines of the plate by tabs cut from the core plate and formed to provide a retaining recess for the shaft. The shaft has a loop between the ends forming a bight on the plane of the damper plate. A retaining member has a head and shank which fits the bight of the shaft and locks it against movement longitudinally, laterally, or away from the plate. The retaining member is held to the plate by a snap-in projection. A method of forming multiple plates from a large composite sheet is described.