The Manuscript Codex * Binding

The material covering the inside surface of a board (and rarely the flaps) in a binding when that material is not part of the structure of the textblock (in contrast to a pastedown). Typically the inner surfaces of the back cover, fore-edge flap and envelope flap are covered separately; sometimes, however, a single continuous sheet of material covers all of them as well as the joints between them. The material covering the inner board may end at the edge of the inner joint with the spine and thus have no direct connection to the textblock, or, it may extend over the inner joint and be adhered onto the outer leaf of the textblock near the spine. In the latter case, the extension of the doublure onto the textblock can be either a stub or a full leaf. In some other cases, the leather used as a spine-lining extends to cover the inner surface of the front and back covers.
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UBL OR. 898