What does it mean to sit in the cemetery and defend Chen?

The Geomantic Survey Compass divides the 360-degree plane into 24 mountains, which are under the jurisdiction of the Bagua District, so it is called "one divination governs three mountains". You said that the mountain in the cemetery is northwest [the northwest is the location of divination, and the three mountains under its jurisdiction are: Xu Ganhai]. The mountain facing the tomb is in the southeast [the southeast is the divination site, and the three mountains under its jurisdiction are: Chen Xun B]. The simple definition is: sit northwest to southeast. The word "concurrently" means that both the mountain sitting and the mountain facing the back are within the "three mountains" under its jurisdiction. If you want to adjust the sitting posture and the back-mountain posture, you can only fine-tune it within this range, and the general principle cannot be moved.