What is "jiaobei"

Jiaobei blocks or moon blocks (筊杯, jiǎo bēi, lit. "bamboo cups") are wooden divination tools originating from China, which are used in pairs and thrown to answer a yes or no question. They are made out of wood or bamboo and carved into a crescent shape. Each block is round on one side (known as the yin side) and flat on the other (known as the yang side). It is one of the more commonly used items found in Chinese traditional religion and are used in temples and home shrines along with fortune sticks, both of which are often used together when requesting an answer from the gods.