The knob is a certificate for mobilizing the army, entering and exiting the customs and courier route, and levying taxes. When it is time to use, both parties must hold their own knob. It can only be effective after the verification of combining two knobs into one piece. The knob is in the shape of a tiger, with the words "Wang Ming = Chuan Lin" engraved on the front. It means that the king orders all the courier stations offering horses, carriages and food to anyone who crosses the stations with a knob. Shou Xian was once the capital of Chu State, therefore it is not surprising that the knob issued by the King of Chu himself was excavated from here.