A mat construction usable in the construction, mining and the like industries wherein timbers or other such materials are tied together into an array. The method includes the steps of connecting the printer controller with the image forming apparatus through a first line which a client sends a print job to the printer controller and a second line which transfers the image data. As a result, etching speed is kept constant. Within the openings, a pair of enclosed chambers overlying the patient’s eyes are defined beneath the respective eye covers.