You may have come across the term 'poison arrow' in fung shui articles but never grasped its meaning. In classical fung shui, 'poison arrow' refers to the sharp edge of a structure that is aimed directly at another and is thereby 'attacking' it. The term sha chi refers to the aggressive energy that is generated.
Looking out of the front door of your home or building, examples of poison arrows would be straight roads or paths that are heading towards you, the sheer edge of a road as it veers off in another direction and the sharp edges of neighbouring buildings. When the entrance of a building or residence is exposed to the sha chi of poison arrows, potentially negative energy that was previously dormant may be activated, resulting in a higher incidence of accidents, miscommunication and even fires.
To rectify the situation, try to relocate your front door if it is in the path of a poison arrow. Some fung shui masters recommend placing ba gua mirrors above (but not on) your main entrance to reflect the negative energy. Where roads are directed straight at buildings, one can place a barrier in front of the entrance to block the sha chi. If you live or work in an afflicted building, it may be best to consult a fung shui professional.