Hardware: five metals. In ancient times, it refers to five metals such as gold, silver, copper, iron and tin, which were artificially processed into metal objects such as knives, swords and works of art. "Wu Yue spring and Autumn" IV "Helu internal biography": "I heard that the king of Yue Yuan often sent Ou Yezi to make five swords,... One Zhanlu, the king of hardware and the essence of the sun." According to the note of "gold, knife, turtle and shell" in the annals of food and goods in the Han Dynasty: "gold is the gold of five colors. The yellow one is gold, the white one is silver, the red one is copper, the green one is lead, and the black one is iron.