flats
An old term applied to papers of various types
which have a well closed, even formation and a
high finish, and which are particularly suitable
for writing purposes. The term derives from the
practice of counting into quires and then folding
the pack. When it became the practice to deliver
writing papers unfolded, they were called "flats."
Today the term is usually restricted to papers
such as tablet paper, as well as to paper with a
smooth, flat finish as distinguished from bond
finish. (197 )