Why do we have to hang a red flag when building a house?

It is said that in order to ward off evil spirits, building a house is very particular. Look at the geomantic omen before building a house, and invite the blind when laying the foundation. When building a house, the host's fire food must be good. It is said that if the host is not satisfied with his food, he will play tricks in the house, such as putting chopsticks and bowls on the beams as appropriate. In short, the feng shui of the house will be destroyed, so the house will be built grandly. Which way the house faces, where the door should be opened, and even the trees planted around the house should be seen by Mr. Feng Shui. Hanging a red flag on the house was originally a piece of red cloth to ward off evil spirits. Later, for convenience, it was gradually replaced by a red list. Later, I simply bought it as a red cloth.

There used to be more gossip hanging on the door frame. Now it is understandable to switch to Cheng Hongqi, where the ground is inserted nearby. But personally, I think the magic of the red flag is at most a lively display. The cornerstone of the housewarming will be covered with red silk and even colorful. Before the bridge was opened to traffic, the towns and villages here would raise funds to worship the bridge, set up bamboo stands to hang lanterns with red flags, light incense wax to burn cypress branches, set a table for sacrificial food and wine, invite a group of old ladies to chant Buddhist scripture, and the laborers in the nearby fields also came to help. A grand gathering of Buddhist firewood, tricycles and hoes. It's very lively, so I haven't been there. I can't say exactly what to do. The flag on the bridge will not be removed after the activity. Probably, when people move to a new house to put wine, they will also put in red flags. Perhaps the national flag has become one of the sacrificial props in the new era? This kind of worship activity of Taoist priests, immortals, monks and bodhisattvas together is really becoming more and more incomprehensible. Therefore, the conclusion is that there is a common principle for hanging red flags and welcoming colored flags, that is, auspicious decoration and lively vision. A reasonable explanation can't stand scrutiny.