Abstract: A controller for trimming copy sheets from a material web in a copying machine is disclosed which utilizes a keypad for easy and error-free input of the widths of document margins without measuring them or converting them from one unit of measurement to another (e.g., metric to U.S. units). The keypad comprises an illuminated bar display one each for the leading and for the trailing document margin. The optical display value of the illuminated bar displays can be set, with the aid of document margin keys provided for that purpose, equal to the width of the document margins, with a digital value corresponding to the selected optical display value being generated and kept available for input to the controller.