Ishiganto are typically carved stones placed at intersections to ward off evil spirits, negative energy or bad luck. In some Asian societies, it is believed that evil travels only in a straight line. So Ishiganto are placed on the gates of homes at T or Y intersections to deflect the energy and prevent the evil from entering the dwelling. (My information comes from Okinawa Living magazine, a free publication to service members here.. fabulous photographs, interesting content, and great design, too!)
As it so happens, our house sits in front of a T intersection, so we have our very own Ishiganto to protect us:
The characters are "ishi," or "stone," in English; "gan," which means "to strike" and "tou," or "dare to." There are a few versions on where the name originated, but Ishiganto is thought to be the name of a god or a mythical warrior. Evil spirits would see the name and flee, fearing the god/warrior's presence and forthcoming wrath...