Most photographs and prints are mounted directly onto a foamcore backing to keep them smooth and flat. A matboard is then added around the edge to enhance the look by giving an attractive visual space between the picture and the frame, and to hold the glass off the surface of the photo. BEWARE! Glossy photos put into a frame where the glass is against the surface, will end up sticking to the glass and the image will be destroyed.
Valuable or limited editions are not stuck down. They are hinged using conservation-grade materials which can be removed, leaving the artwork returned to its original state. UV protective glass is recommended for limited editions.