cut to show proof (bookblocks)

Book blocks the edge of which is cut to a depth that leaves the shortest leaves uncut, showing, on handmade paper, the deckle edge of the sheet. This term is specific to books with leaves of handmade-paper. Cutting to show proof was a sign of careful work, and was intended to leave proof (témoins in French) that only the minimum amount necessary to leave a clean edge had been removed from the margins of the leaves.