Find half the distance between the spine and the medial edge of the scapula.
Feel for the highest point of the paraspinal muscles.
Find the medial edge of the scapula. This is 1.5 cun lateral to the spine.
Use your handsbreadth to find 3 cun. Then take half of that distance.
UB 27 and UB 31
UB 28 and UB 32
UB 29 and UB 33
UB 30 and UB 34
Here's an interesting quiz for you.