For the divination, the bones or shells would be heated around holes which had been drilled into them. This would cause single irregular transverse cracks to appear, which the official diviners would interpret to judge whether they implied good or ill omen.
占卜時燒灼甲骨上鑽過的部位，就會沿著橫的方向出現一條不規則的裂紋，這就是卜兆，卜官依此斷定吉凶。