What did the ancient jade turtle do?

Jade turtle is a round carving, which is divided into two parts: back armor and belly armor. The tortoise is hollow, and the tortoise pattern in the shell is very realistic. The carapace and the carapace are connected by holes and dark grooves. This jade turtle and rectangular jade piece were unearthed at the same time, reflecting the close relationship between them and should be used as a divination tool. It should be no problem to say that the jade piece is moderate and square. Taking eight numbers as the dimension of heaven and earth, since

Obviously.