What do you mean by "iron red flag"

The third day of the first month is "Red Mouth", also known as "Red Dog Day".

In southern China, "Red Mouth" was posted on the morning of the third day of New Year's Eve. I think this day is easy to quarrel and not suitable for New Year's greetings. The so-called "red mouth" is usually made of a piece of red paper with a length of seven or eight inches and a width of one inch, with some words of safety and good luck written on it, which is pasted on the top of the front and back doors, and another piece of paper is placed on the garbage so as to pick it out and throw it away.

In a word, posting "Red Mouth" is to make people feel that they can go in and out safely all year round, without quarreling with others or all kinds of unfortunate disasters, and they can make money and make everything smooth at home.