The oldest references to the Chinese sailing vessel known as the junk date back to the Han Dynasty (220 BCE-200 CE), although it is generally believed that the junk was in use even earlier. The term junk has many origins, including roots in the Portuguese junco, the French junque, the Dutch jonk, the Malay jon, and the Javanese djong. The junk is identified by its high stern, projecting bow, and square linen sails. The sails are spread and contracted in an action similar to that of collapsible Venetian blinds. Instead of a keel, the junk has a large rudder. Junks were integral in Chinese trade and exploration up until the nineteenth century.