This side view of the common press is particularly useful for showing how the frisket folds down over the paper on the tympan, which then folds down over the imposed forme for printing. The pressman (standing facing us) would then roll the forme under the platen (barely visible hanging between the upright cheeks) and then reach across to pull the lever to lower the platen, creating the pressure to transfer the ink from the type to the paper.
Jean D’Alembert, Robert Bénard, Denis Diderot, Recueil de planches, sur les sciences, les arts libéraux, et les arts méchaniques. [Encyclopédie.] Paris: André le Breton et al, 1769. (vol. 7, plate 15)
Smithsonian Libraries, AE25 .E53X 1751 Plates (public domain)