Paper size a number of different sizes were defined for large sheets of paper, and paper sizes were defined by the sheet name and the number of times it had been folded. Thus a full sheet of "royal" paper was 25 × 20 inches, and "royal octavo" was this size folded three times, so as to make eight sheets, and was thus 10 × inches. Imperial sizes were used in the United Kingdom and its territories. These sizes are no longer commonly used since the UK switched to ISO sizes. Many of these sizes were only used for making books (see bookbinding),
Folded leaflet pattern in which the folds are parallel and in the same direction, so that a kind of spiral is produced. The letter fold is a parallel fold. Two or more panels of the same width of the folded signature are folded around one panel. When the signature is folded twice, there are three panels on each side (six pages); with a tri-fold, the result is four panels on each side (eight pages). To allow proper nesting of panels that fold in, inside panels are usually 1/32" to 1/8" smaller than outer panels with the inside end panel being the smallest.