What does the nine-door eight-one clock code mean?

Refers to the tools and forms used by Beijing to tell the time in Ming and Qing Dynasties. The clock is a clock, the dot is a dot, and both the clock and the code are tools for telling the time. There are nine gates in the inner city of Beijing. Among the nine doors, there are eight doors with a "temple" hanging on the building, and one door with a "bell" hanging on the Chongwen door, so there is a saying of "nine doors, eight codes and one bell". Specifically, the first point is to remind everyone of the time to open and close the city gate. When opening and closing the city gate, the bell rings to remind everyone that it's time to open and close the city gate, so we should hurry up, or we won't be able to enter (leave) the city.