The Ugra Screen Ruling Indicator is used to determine the screen ruling. The scale indicates the screen ruling in Lines/inch as well as in Lines/cm.
The Screen Ruling Indicator works similarly to a ruler. For this purpose, lines are printed on the foil, which show an interference or moireé when placed on a printed matter. If you turn the screen ruler in a corresponding direction or angle so that the lines converge at the edge, you can read the numerical value on the scale in lines/inch or in lines/cm. The numerical value indicates the screen ruling in which the printed matter was printed.