ake a long time to do so. Such
sheets are called "imperfections," and the printers usually keep a
number of "overs" in order to make good such imperfections as may
occur.

FOLDING

Books received in sheets must be folded. Folding requires care, or the
margins of different leaves will be unequal, and the lines of printing
not at right angles to the back.

Books of various sizes are known as "folio," "quarto," "octavo,"
"duodecimo," &c. These names signify the number of folds, and
consequently the number of leaves the paper has been folded into.
Thus, a folio is made up of sheets of paper folded once down the
centre, forming two leaves and four pages. The sheets of a quarto have
a second fold, making four leaves and eight pages, and in an octavo
the sheet has a third fold, forming eight leaves and sixteen pages
(see fig. 2), and so on. Each sheet of paper when folded constitutes a
section, except in the case of folios, where it is usual to make up
the sections by inserting two or more sheets, one within the other.

Paper is made in several named sizes, such as "imperial," "royal,"
"demy," "crown," "foolscap," &c. (see p. 283), so that the terms
"imperial folio" or "crown octavo" imply that a sheet of a definite
size has been folded a definite number of times.

[Illustration: FIG. 2.]

Besides the traditional sizes, paper is now made of almost any length
and width, resulting in books of odd shape, and the names folio,
quarto, &c., are rather losing their true meaning, and are often used
loosely to signify pages of certain sizes, irrespective of the number
that go to a sheet.

On receipt, for instance, of an octavo book for folding, the pile of
sheets is laid flat on the table, and collated by the letter or
signature of each sheet. The first sheet of the book proper will
probably be signature B, as signature A usually consists of the
half-title, title, introduction, &c., and often has to be folded up
rather differently.

The "outer" sides, known by the signature letters B, C, D, &c., should
be downwards, and the inner sides facing upwards with the second
signatures, if there are any, B2, C2, D2, &c., at the right-hand
bottom corner.

The pages of an octave book, commencing at page 1, are shown at fig.
3. A folder is taken in the right hand, and held at the bottom of the
sheet at about the centre, and the sheet taken by the left hand at the
top right-hand corner and bent ove