XX. The City-Gate Formula: Principles for Compliantly Receiving Qi from the Side

1. What the City Gate Is

What Xuankong calls the "city gate" (chengmen) borrows the idea of a water mouth or side gate outside a city's main gate, taking in qi from the side to support the main facing. It looks at whether the trigram positions on either side of the facing point have a usable water mouth or active qi, and judges, by a set of rules for starting the stars, whether flourishing qi can be gathered there. Not every side door counts as a city gate, and one cannot simply cut an opening in a wall and "seize the period" on a whim.

Commercial shops commonly have a side door, a corner in a mall corridor, an escalator landing, or a parking entrance, which can genuinely form a side approach of qi. When surveying, first record which trigram they fall in relative to the facing point, how strong the actual foot traffic is, and whether they fall within the shop's own controllable range, and only then judge them according to whichever Xuankong convention is being used. If there is truly no door and no water on the side at all, then however good the city-gate star looks on paper, it has no form to draw on.

2. The Principle of the Main City Gate and the Secondary City Gate

Tradition commonly divides the two trigram positions adjacent to the facing point into a main city gate and a secondary city gate, with the specific determination and method of plotting depending on the period chart and the cycle-dragon. This article does not offer any exaggerated secretly transmitted formula, and instead emphasizes what can be recomputed: mark the facing point, fix the adjacent palaces on the left and right, start the city-gate star according to the rule, judge whether it currently governs, and then verify it against the real water mouth. If any one of these steps is unclear, no absolute conclusion should be given.

For a city gate to be usable, the side approach of qi generally needs to be clear, gentle, and sentient, without disrupting the main qi of the true facing. If a side door's foot traffic, though heavy, rushes straight at the back door, brings noise, and opens a security gap, one cannot judge by the flourishing star alone. A side door can take on the role of drawing traffic in, while the main door still needs to form the point of recognition and gathering.

3. The Compliant Boundary for Taking Qi Through the City Gate

One must never cut into a wall without authorization, alter a load-bearing structure, occupy a fire lane, or encroach on a public corridor in pursuit of an auspicious city-gate position. Whether a door can be opened is decided by planning regulation, structural engineering, the property manager, and fire code. The divinatory arts can only offer a traditional comparison among the door positions that are legally available. A so-called "period-activating door" opened without approval carries real risk and undermines the shop's long-term stability.

Where a door cannot be opened, one can still adjust the primary-versus-secondary use, the orientation of displays, and the point of greeting customers within the existing legal openings — but one should not pretend that a lamp or a fan is equivalent to a real water mouth. A lamp can activate, and a fan can guide qi, but their weight is not the same as a door and path that continuously admit customers.

4. The City Gate Must Not Be Made to Look Like a Secret Transmission

The city-gate formula does differ in detail across different sources, and one should clearly choose which version is being used and lay out the steps. A verdict of "transmitted only to those with the right affinity" cannot be independently checked, and easily lets a calculation error be dressed up as a secret. This article invents no formula and fabricates no lineage of transmission — it only explains the theoretical structure and the boundary of what is safe and legal.

If two different city-gate conventions produce different results, they can be set side by side as candidate A and candidate B, giving priority to whichever direction both agree on and which also has a real form on site; where they conflict, no major action should be taken. Traditional knowledge can retain genuine differences between schools — there is no need to pretend there is only one universal answer.