Ménshén is the deity of doors, gates and passages in Chinese religion. Various historical persons are worshipped as incarnations of Menshen. They are usually painted or affixed pictures on each of the two wings of a door.
The Chinese custom of representing them on doors has a history of many centuries. In the Han dynasty, people believed that peach wood has spiritual properties and can ward off evil spirits so they started making auspicious carvings on peach wood and hanging them around their homes. Following the invention of paper, paper gradually replaced peach wood as people started drawing and writing on paper instead. In earlier times, Shentu and Yulü were the most common choice as Menshen. In the Tang dynasty, the two generals Qin Qiong and Yuchi Gong became door gods when Emperor Taizong ordered portraits of them to be affixed on gates. Other folk heroes and mythological figures were subsequently added to the Menshen pantheon.
The door gods usually come in pairs, facing each other; it is considered bad luck to place the figures back-to-back. Portraits of Wei Zheng or Zhong Kui are used on single doors.