There are 3 basic types of Ba Gua mirrors – Concave, Convex, and Flat ...
Each is used to negate opposing / attacking / negative Energies which may come from outside ...
They are usually either hung outside a window, or placed on the inside of a window facing out.
Never face a Ba Gua mirror into the house as its energies are simply too strong for interior use.
Flat mirrors simply bounce energies back to their source, impacting anything else they come across ... so be sure you are not affecting any ‘innocent bystanders’.
Concave mirrors ‘trap energies’ by capturing and inverting the image they reflect.
This is often used when many buildings are around, but not all necessarily negative – by trapping the energies you ensure that there is no contamination ... but these mirrors have to be cleansed every two weeks [at the change of the Moon Cycle], so the negative energies may be released appropriately. This is done by placing the mirror flat on the ground or on a surface so it reflects the sky ... leave it there for a minimum of three days, or until it is needed.
Convex mirrors are usually the best as their shape gently moves negative energies aside, without reflecting it back to the source ... just dissipating it.