Yet a press did not churn out copies of a book on a daily basis: crucially, printing was done by the sheet. After setting up the metal type in a frame, the printer would print a certain number of copies of one sheet; then the frame would be broken up, the type washed, and re-set for the next sheet, and so on. A book could thus be on the press for six months, and the printer would not have a single product to sell, given that the book was never ready until the final sheet had been printed.

Andrew Pettegree, Arthur der Weduwen, The Library- A Fragile Hist…, loc. 170