If you have a main door that falls into the west in 2018, you should place a Ba Gua mirror above the door on the outside to deflect the negative energy. There is no need to hang it if the door is never used. Cleansed of negative energy and positively empowered with Sha Chi. Generally, they should be used when you have negative Sha Chi outside your home or office like a lamp post, telephone pole etc. These are the best quality and made from wood, you should never use plastic ones as they hold the negative chi longer and can be dangerous.