A system is disclosed for sealing a manufacturer's joint and/or the ends of a customized box. The system includes at least a first arm spaced apart from a second arm. The arms are arranged so that an end flap of a box blank can be inserted between the arms to align the box blank relative to the arms and secure and maintain at least two side panels of the box blank in an adjacent position to form a manufacturer's joint. Methods for forming and sealing a manufacturer's joint and/or the ends of a customized box are also disclosed. Such methods, are designed to, for example, reliably form, close, and seal the manufacturer's joint and/or the ends of a customized box in a simplified manner.