backing

Stone, brick, etc. forming the unexposed or unfinished wall behind the face stones; generally, backing is of an inferior or cheaper class of material. Backing also is used to describe the backfill of a retaining wall. 2. A bevel given to the outer and upper edge of a hip rafter in order to allow sheathing to fit the top of the rafter without leaving a triangular space between it and the lower side of the roof covering. 3. A narrow wood strip fixed to the corner of a framed partition to provide a nailing surface for finish materials. (Phillips, 1994)