The part of a mat made from a solid piece of mat board, which functions as a protective support for works of art on paper. This term is sometimes confused with a backing board, which serves a different function. See also Mounts, mats.
(Back Mat or Bottom Mat) The mat in direct contact with the verso (back) of the artwork and to which the artwork is typically attached. Backing Board: The stiff foam board, corrugated paper or plastic board inserted into the frame to protect its contents from p hysical and atmospheric damage.