What does it mean that the house is between two hexagrams? Why is this unlucky?

When measuring a house, the red line of the compass is just between the hexagrams, and such a house is a hexagram. If it happens to be pressed between mountains, it is a gap.

Houses with divination account for about 2% of the total number, and houses with joints account for about 16%-20% of the total number.

In both cases, the house is a haunted house and should be avoided. Houses for divination should also be treated with caution and it is best to avoid them.