1. regulate,
2. medicate or
3. arbitrate
the chart to maintain its balance. When the Useful god is strongly rooted and protected, then the chart is superior.
In the above example, what do you think is the Useful god?
This is a weak bing day master born in the si hour of a winter month. In the classical method, we also look at a chart pictorially to see whether an image can be formed. Bing represents the sun while gui represents the cloud. The sun is most useful when born in the chen or si hours because the morning sun is not too hot and helps to warm the earth. What happens when this sun is blocked by the cloud?
Imagine the sun in the cold winter morning being blocked by the cloud. What do we need here?
Yes, we need the fire place which is represented by the ding fire. Ding fire is the Useful god as it is needed to regulate this chart. Now, on the technical side, the ding fire needs to be protected by the wood stars. Otherwise, the strongly rooted water stars will counter it. So, the primary Useful god is the ding fire while the secondary Useful god is the jia or yi wood.
Hence, both the technical and classical methods can be applied simultaneously.