Hello, according to Feng Shui, it is generally used to ward off evil spirits. Coins are made of metal, and they pass through the hands of countless people in circulation, so they are full of yang energy, so there are often people on the windowsill. Or place coins under the threshold to block external evil spirits. Placing three means obtaining the energy of the three talents of heaven, earth and man, and the effect of blocking evil spirits is better. However, under normal circumstances, people will choose ancient copper coins, but if they cannot find ancient coins at the moment, they usually use modern coins as temporary substitutes.