What does it mean to go out of the hexagram, out of the line, and to join the mountain?

What does it mean to go out of the hexagram, out of the line, and to join the mountain?

There are eight hexagrams on the compass, and each hexagram has three mountains, totaling twenty-four mountains. The cross line on the compass overlaps between the hexagrams and the hexagrams, which is called "out of hexagrams" and commits a fierce evil.

The cross line overlaps the mountain and the mountain in a hexagram, which is called "exit line".

Each mountain is fifteen degrees, and it is divided into five grids, one grid for every three degrees. The cross line falls within the middle nine degrees is "positive mountain forward", and the one that falls within three degrees on both sides is "Jianshan Jianxiang". The layout of the plate is different from the positive mountain forward.