Why does someone hang a small mirror outside the window? What did Feng Shui say?

It is unlucky to think that mirrors can ward off evil spirits. A flat mirror is a reflection. It's useless. Actually, hanging a mirror is very particular. For example, the Eight Diagrams Mirror can be divided into plane mirror, convex mirror and concave mirror. Gossip is a foundation. Protect the victims from being washed away with the yin and yang elements of gossip. That convex mirror is mostly used to break evil spirits. Concave mirror is often used to break like a sword and arrow. Chop, wait.