I have a customer inquiring about dimensional letters to be used to number buildings in a complex. I have traditionally only worked with cutting vinyl, banners, signs, etc. and have no experience here. I want to find a wholsaler to provide this service for my shop. But I have no idea what material is used. This customer wants these adhered to a glass transom window above the entry doors of the building - ideas? This would be exterior application directly to the glass. Any advice is appreciated!