By driving a nail into a sacred tree at Ushi no koku (midnight from 1 am to 3 am,) it was believed that the barrier between worlds would be broken and the evil-wreaking gods (devils and specters) would be summoned from the Tokoyo (eternal night kingdom of God), possessing the summoner and cursing whoever they hated.
丑の刻（深夜）に神木に釘を打って結界を破り、常夜（夜だけの神の国）から、禍をもたらす神（魔や妖怪）を呼び出し、神懸りとなって恨む相手を祟ると考えられていた。