the usual impression cylinder 15 and backing roll 16 are also shown on the plate cylinder there are four sets of printing plates each printing plate is in two semi cylindrical portions 17 and 18 and these semi cylindrical portions of the printing plate are held on the plate cylinder 13 by torsion cylinder plate locks 19 and 20 the direction of rotation of the various cylinders is indicated by arrows on the ends of the cylinders in fig2 the way in which the printing plate halves 17 and 18 are secured to the plate locks 19 and 20 is shown in more detail one of the plate locks 19 is shown together with parts of the surrounding structure the plate cylinder 13 is set to rotate in the direction of the arrow 21 in fig2 the leading end of printing plate half 17 is illustrated and the trailing end of printing plate half 18 each printing plate half comprises a substrate respectively 22 and 23 of a resilient flexible plastic material as shown in fig2 the leading end of substrate 17 is formed with a first bend 23 and a second bend 24 the first bend 23 brings the portion 25 of the substrate back underneath the printing plate and the second bend 24 brings the portion 26 of the substrate right at the leading edge back in the original direction of the substrate as can.