Abstract: A process of retrofitting an existing window that uses a gasket to secure a sacrificial member and a glazing. The sacrificial member forms a replaceable protective barrier between the glazing and occupants of a vehicle such as a bus. The gasket is traditionally used to secure the sacrificial member and the glazing to the window. Over time, after several removal and re-installations during replacement of the sacrificial member or the glazing, the gasket typically becomes unfit for subsequent use. The gasket is replaced with a rigid retainer member that fits into an existing recess that receives the gasket. The retainer member secures the sacrificial member and the glazing to the window so as to permit repeated changes of the sacrificial member without removal of the retainer member.