Gods, the convex surface is positive and the plane is negative. Before asking for a sign, you should silently ask the Buddha if it is allowed to ask for a sign, and then vote for two gods at the same time. If it is a yin-yang "auspicious symbol", you can draw lots; If it is a double-yang "laugh" or a double-yin "anger", it must be thrown again. After the lottery, you need to pray again and throw it again until you throw an "auspicious sign" to prove that the drawn sign is correct, and then you can interpret it.
This custom should have originated in eastern Fujian. When I traveled to Taiwan Province Province, there was something like this in the temple.