An apparatus and method for applying reference or grid markings to wallboard during the manufacturing process is disclosed. Reference or grid markings are applied to one sheet of cover paper at a location between the originating cover paper rolls and the cover paper creaser or creasers. This is accomplished by locating and aligning multiple print heads across the width of the continuously passing cover paper, such that markings are ejected onto the cover paper in a specific and coordinated fashion. In addition to using any suitable commercially-available computer equipment to coordinate printer head activity, this function is accomplished by attaching each print head to a common horizontal support element and provide individual adjustments that are perpendicular to, and with the directional flow of the passing cover paper.