The book is now stripped of its former binding, and the next step is to take it apart, signature by signature. A signature is that number of leaves which make up one sheet of the book in hand. Thus, an octavo volume, or a volume printed in eights, as it is called, has eight leaves, or sixteen pages to a signature; a quarto four leaves; a duodecimo, or 12 mo. twelve leaves. The term signature (from Lat. _signare_, a sign) is also applied to a letter or figure printed at the foot of the first page of each sheet or section of the book. If the letters are used, the signatures begin with A. and follow in regular sequence of the alphabet. If the book is a very thick one, (or more than twenty-six signatures) then after signature Z, it is customary to duplicate the letters--A. A.--etc., for the remaining signatures. If figures are used instead of letters, the signatures run on to the last, in order of numbers. These letters, indicating signatures are an aid to the binder, in folding, "gathering," and collating the consecutive sheets of any book, saving constant reference to the "pagination," as it is termed, or the paging of the volume, which would take much more time. In many books, you find the signature repeated in the "inset," or the inner leaves of the sheet, with a star or a figure to mark the sequence. Many books, however, are now printed without any signature marks whatever. To return: in taking apart the sheets or signatures, where they are stuck together at the back by adhesive glue or paste, the knife is first used to cut the thread in the grooves, where the book is sewed on cords or tape. Then the back is again soaked, the sheets are carefully separated, and the adhering substance removed by the knife or fingers. Care has to be taken to lay the signatures in strict order or sequence of pages, or the book may be bound up wrongly. The threads are next to be removed from the inside of every sheet. The sheets being all separated, the book is next pressed, to render all the leaves smooth, and the book solid for binding. Formerly, books were beaten by a powerful hammer, to accomplish this, but it is much more quickly and effectively done in most binderies by the ordinary screw press. Every pressing of books should leave them under pressure at least eight hours.