Illustrated glossary of the parts of a manuscript binding. From Michelle Brown, Understanding Illuminated Manuscripts: A Guide to Technical Terms (London: The J. Paul Getty Museum in association with the British Library, No mention of copyright.
This week's word is 'pastedown'. A leaf is pasted onto the inside of a board to conceal the channeling and pegging and other mechanics of the binding. Pastedowns are often formed of fragments of earlier manuscripts that were considered dispensable.