The moist paper was then inserted into a hinged cover above the type-area with the letters and was fixed with pins. Then the cover with the paper and the frame was positioned over the locked-up forme of type and under the plate of the press, the platen. The platen was made to descend firmly and evenly onto the paper

Positioning of a page - Woodcut of J. Amman 1568 (detail) Note the pins going through the paper

This transferred the ink onto the paper. The pricks from the pins used to fix the front side paper or vellum during the printing process could be used to align the reverse side during printing.