One of the three functions of the bill of lading is to act as evidence of the contract of carriage. It is not necessarily the contract itself which may be verbal or may be made up of protracted correspondence, however, it is con sidered best evidence of the contract. When the bill of lading is transferred to a third party, it may become the contract. Many contracts are port to port and are between the shipowner or shipping line and the shipper of the cargo.