What do you mean by vertical direction?

Orientation is one of the most important things in geomantic omen. In the geomantic omen of Kong Xuan School, there are two points: attention and simultaneous attention. Let's talk about attention first: it refers to the line that crosses the red vertical line outside the compass and presses the center of a word without any deviation. The main purpose of Li Zhengshan's positive orientation is to take the pure spirit of mountain orientation without mixing other hexagrams or words.