Your shipping order (S/O) will be the most important document you receive when you use the services of a container freight company. This piece of paper will list all of your important details and all of the details about your container. It will have the vessel number and your container number, as well as other information that will be used for processing your order. You can use this document to track your order through the internet or a major metropolitan newspaper. When your shipment arrives, it serves as proof that the container is yours and helps speed you through customs.