In a method of producing a molding die for use in producing honeycomb structure bodies, a reference position is determined as a relative position on a workpiece between a pillar of a high-pressure water jet and a reference hole. The apparatus also has a pivotally mounted scraper adjacent the bottom roller, auxiliary rollers disposed behind the scraper, two fences that run along the sides of the loading deck, and cutting blades for separating the different sections of the bag for collection on the rollers. The insulator layer is plasma etched either before or after the vapor deposition of the second conductor to define in the insulator layer a via hole through which at least a portion of the first conductor is exposed.