Glass spacers - Framespace and Econospace are two brands of plastic spacers for framing - try for large orders, or Light Impressions for smaller lots at a higher price. Econospace is a pressure sensitive strip that attaches to the glass - in either clear or black. Framespace is a double channel design that will put from 1/8" up to 3/4" of space between print and glass - comes in clear, black and white. A "friendly" local frame shop may be able to show you samples.