It was considered that by hammering a nail into a sacred tree at ushi no koku (around two to four in the morning, late in the night) the boundary marking the sacred realm would be broken, god (evil or yokai) that brings about misfortune would be summoned from tokoyo (god's world with eternal night), and the ritual performer would gain a supernatural power to hex the person against whom one held a grudge.
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。