Toshiba FIERY GA-1121 - Manual (Page 172)

A
A-2 Basics of Imposition
The printed sheet is folded into something resembling a booklet with connected pages.
The folded sheet, called a signature, is then trimmed to the finished size.
For pages to appear in normal reading order and position in the final booklet, their
ordering and positioning on the sheet must differ from the normal book-reading order.
You can demonstrate this for yourself using an ordinary sheet of paper.
T O MODEL AN EIGHT - PAGE BOOKLET
1. Fold the paper in half horizontally.
Fold the top edge of the sheet down to meet the bottom edge.
2. Fold the paper again vertically.
Fold the left edge of the sheet over to the right edge. Now you have a miniature version
of a signature.