What was tortoise shell mainly used for in Shang Dynasty?

Tortoise shell engraved with Oracle Bone Inscriptions comes from Shang Dynasty and should be mainly used for divination and sacrifice.

The font inscribed on the tortoise shell of Shang Dynasty is called Oracle Bone Inscriptions. Oracle Bone Inscriptions, also known as "Wen Qi", "Oracle Bone Inscriptions" or "tortoise shell and animal bones". Oracle Bone Inscriptions recorded and reflected the political and economic situation of Shang Dynasty, mainly referring to the words carved on tortoise shells or animal bones by the royal family in China in the late Shang Dynasty (14 ~ 1 1 century). After the demise of Shang Dynasty and the rise of Zhou Dynasty, Oracle Bone Inscriptions was still used for a period of time, and it was the earliest known systematic writing form in China. It inherits the original carving symbols and inspires the bronze inscriptions, which is the key form of the development of Chinese characters and is called "the earliest Chinese characters". Modern Chinese characters evolved from Oracle Bone Inscriptions.