In geomantic omen, compasses are used to determine the orientation of buildings and the direction of water outlets. When selecting the nozzle, the compass dial will be used for measurement. The sky disk refers to the circle in the middle of the compass, which is often referred to as the direction of the twenty-four mountains.
The method is to aim the center of the compass at the nozzle and read the position on the sky disk, that is, the position of the nozzle. The building is in the direction of the dry mountain, so the water outlet should be in the direction of the dry mountain, which is the southeast of the compass.