What is a mountain and a vein?

ok. This is a term (or proverb) in traditional architecture in China. ), which is the form of the shape outline of the roof. "Starting from the mountain" means that the longitudinal corners of the roof are raised, and "falling veins" means that the second and third purlins on the roof on both sides of the horizontal slope are lowered by a certain height to form a height difference.

it's easier to understand to look up the map in detail. . .

Ancient architecture emphasizes geomantic omen, but these two are just architectural techniques, and it is enough to talk about geomantic omen.