Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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A sheet folded to form 12 leaves or 24 pages. Although two parallel folds followed by two right angle folds will produce this gathering, the more common method is to print the sheet 12 up on each side, and then cut the sheet into 2 sheets of 8 and 4 leaves. The larger sheet if folded three times, and the smaller twice, the latter being insetted. The insetted section may be given a sub-signature, e.g., B1 or B*, which the binder notes when binding the book. If the printer imposes 2 rows of 6 pages (on each side), the result is known as "long twelves," but if 3 by 4, "short" or "square" twelves. Where the width of the leaf is greater than the height, the term "broad twelves" is used. Also written 12mo or 12. See also: OBLONG .

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