The South Gate of Heaven was called Tianmenguan in ancient times. Since Mount Tai represented heaven in ancient times, the top of Mount Tai was the location of the Heaven.
There are four gates in the Heaven: East, West, South, and North. This gate faces south, so it is called "South Gate of Heaven". It is also the main entrance to the Heaven, leading directly to the Lingxiao Palace of the Jade Emperor, which is above the Nine Heavens (some say it is the Thirty-Six Heavens). In many myths and legends, the gods guarding the South Gate of Heaven have many names, such as the King of Growth, Wang Lingguan, the Four Marshals of Ma, Zhao, Wen, and Guan, Zhang Tianshi, and the Great General of Xuantian Shenwei (who was personally appointed by the Jade Emperor).