Page:De Vinne, Invention of Printing (1876).djvu/541

Rh who said that the printers of Mentz printed three hundred sheets a day. This seems a small performance.

The accurate register of the first books was produced by placing the white sheet on four fixed points which perforated the four corners of the leaf when the first side was printed. In printing the back of the page, the half-printed sheet was hung on the same points, from the same point-holes, and was impressed in the same position. Blades notices the four point-holes in some of Caxton's books, and it is probable that the mysterious pin-holes in other books are the marks of points. It was soon discovered that register could be had with two points, which were placed in the centre of the sheet where the marks would be hidden by the binder.