Introduction: Seal is a professional production of custom-made seals that are loaded into a container and are properly closed after the door is fitted by a particular person. Zhenlang seal seal according to the different personnel can be divided into customs clearance, commodity inspection and business seal. Once the seal is properly locked, unless the violent damage (ie, cut) can not be opened, the damaged seal can not be reused. Each seal has a unique number. As long as the appearance of the container is complete and the container door is properly closed and the seal is sealed normally, it can be proved that the container has not been opened in private during the transport. The situation in the box is supervised by the boxer at the time of packing.