Due to the stickiness of the ink, the imprinting is fixed within a certain range. During the printing process, the squeegee blade is always in line contact with the screen printing plate and the substrate, and the contact line moves with the squeegee. Because of the distance between the screen plate and the substrate, the screen printing plate produces a reaction force against the squeegee blade by its own tension, which is called resilience. Due to the effect of resilience, the screen plate and the substrate are brought into movable line contact with each other, but the other portions of screen printing plate are separated from the substrate. In this way, the ink and printing screen undergo a cracking motion, which ensures the dimensional accuracy of printing and avoids soiling substrates. When the squeegee is scraped across the entire plate, it is raised along with printing screen plate and then scrapes ink back to its original position. This is a printing stroke.
Although being widely used, Frederick Marryat signal flag only contains figures. The history of letter flags goes back to 1800 by Home Popham’s "Telegraphic Signals Or Marine Vocabulary", which appeared in 1803 with a large number of different language versions.
The famous fleet commander Horatio Nelson, as the pride of British Royal Navy, printed a well-known signal: “ENGLAND EXPECTS THAT EVERY MAN WILL DO HIS DUTY” on his flagship on October 21, 1805 before decisive battle with the French fleet in Cape Trafalgar, which was used to encourage the morale of the officers. This message is exactly using Home Popham’s letter of flag signals.