Mirror, mirror on the wall
In Southeast Asia it is not uncommon to see ba gua mirrors hanging above apartment doors. These mirrors are used to deflect attacking, or negative, energy and should be used only outside the home.
Ba gua refers to the collection of eight trigrams (line formations derived from The I Ching Or Book of Changes) that reflects the yin and yang energies in the universe. On ba gua mirrors, the trigrams are arranged in the Former Heaven Sequence, with heaven (three unbroken lines) at the top and Earth (three broken lines) at the bottom. This is the correct way to hang a mirror. If it is hung the opposite way, it could attract unwanted yin, or spectral energy.
Ba gua mirrors can also be convex or concave. Convex mirrors are able to deflect attacking energy from structures such as sharp edges or pillars. Although concave mirrors are also able to deflect negative energy, they can also concentrate the energy and redirect it back, thereby injuring others. Cases have arisen where neighbours have noticed a convex ba gua mirror opposite their front door and unwittingly retaliated by hanging a concave ba gua mirror. Outside Asia, some fung shui consultants prefer to use plain mirrors due to concerns regarding cultural and religious sensitivities.