Worshipping Door Gods is an important custom among the Chinese during Spring Festival, the Lunar New Year. Door gods are pictures of deities posted on the door outside and inside the house. They are expected to keep ghosts away, to protect the family and to bring peace and good fortune.
A typical Chinese house has a huge front gate/door with two wings that open in the middle. The door gods always come in pairs facing each other. There is the main door god, the secondary door god, the back door god and the wing room door god. And it is considered bad luck to place the figures back-to-back. Besides, The image of a chubby baby is considered as a wing room door god, symbolizing good luck, longevity and fertility.
Placing Door Gods on the external doors of houses is a time-honored tradition dating back to the Tang Dynasty (618 - 907 AD). The then Emperor Taizong is said to have fallen ill, and had a dream in which ghosts came to the palace in search for him. He recounted this tale to his officials the next day, and the story quickly spread through the Imperial Court: such matters were taken rather seriously at that time. From then on, two of the emperor's top generals, Qin Qiong and Yuchi Gong, both of whom had fought with hime to establish the Tang dynasty, stood outside guarding the emperor's bedroom door. Therefore, the emperor was ablt to sleep soundly in the knowledge that he was protected by these two generals, and had no further dreams of the ghosts. The tale soon became widely known, and in their eagerness to share the protection of these "Door Gods", the common people made their own paintings and placed them on their doors. The tradition has continued ever since.
The main door god comes in several different forms. The earliest door gods were Shen Shu and Yu Lei. They were assigned to guard the entrance to heaven under a magical peach tree that grew on Mount Tu Shuo, where they either let people pass into heaven, or rejected them, based on their life's deeds. The Jade Emperor decreed that those who had done evil should be caught, bound and thrown to the tigers. Zhong Kui the ghost-catcher was a door god in the Tang Dynasty. Strictly speaking Zhong was not a real door god but a mythical ghost-catcher and he is often called the "backdoor general".
Nowadays, the most common door gods are Chin Shu-pao and Yuchi Gong, who became popular during the Yuan Dynasty. Chin has pale skin and usually carries swords; Yuchi has dark skin and usually carries batons. According to a Tang Dynasty legend, the emperor ordered the two generals to guard his door while he slept to keep away a ghost that had been bothering him. With the two men standing guard at the door, the emperor slept peacefully. The next day, the emperor, not wanting to trouble his two loyal generals, called on men to hang portraits of the two men on either side of his door. Ordinary families soon adopted the imperial custom, putting woodblock prints of the ever-vigilant generals on their front gates in the hope of attracting good luck and fending off evil spirits.