When measuring the sitting direction, if the compass pointer points within 3 degrees to the left or right of the hexagram line, it is called double hexagram; Pointing to the left or right of the riding seam within 3 degrees is called a double line. When there are both hexagrams and lines, it is the so-called mountain and direction.
There are both hexagrams and deeds, which is ominous. In order to avoid bad luck, we can't use the usual flying star method, but we need to use substitution hexagrams to help us judge.