In ancient my country, handcuffs were called "梶" (gu, to sound), and shackles were called "桎" (zhi, to sound). They were both made of wood at first. During the archaeological excavation of the Shang Dynasty ruins, Pottery figurines with shackles have been found: female prisoners were handcuffed on the chest, and male prisoners were handcuffed on the back. It can be inferred from the perfection of its shape that the "shackles" should have existed earlier, that is, in the Xia Dynasty.