The junk is a style of Chinese ship that came into use in c.220 B.C.E. and remained common through the 19th century C.E. Junks were not only ships of exploration, they were also ships of trade, and sometimes ships of war.
Junks were designed to be very sturdy, and incorporated several watertight compartments. This meant that if a hole was made on the outside of the ship, there would be another compartment to catch the water, leaving it sealed off from the rest of the ship. These compartments also created a strong internal structure to the ship. Junks were typically made of teak wood. Junks were fitted with stern-mounted rudders. It is, in fact, a junk that is the earliest known example of mounting a rudder on the stern; there is a clay sculpture of a junk dating to the 1st century C.E. depicting a stern-mounted rudder.
The biggest difference between early examples of Western sails and Chinese junk sails was the shape. Chinese junks were not square-rigged, rather, they had elliptical, curved sails, which were reinforced with inner battens made of bamboo. Because the bamboo kept the sails strong, less rigging was needed. It also prevented the sail itself from fraying and rotting as quickly as it would have without the bamboo battens. Junks of different sizes had different numbers of masts.