A Main line is the smallest connected structure that explains the question you actually asked. First identify the problem palace and define its real-life domain. Then compare the House combination around it, Three Parties and Four Uprightnesses, the opposite palace, relevant Four Transformations, repeated evidence, time layers, and observed facts. A line deserves priority when it connects several relevant signals through a clear mechanism and survives practical counterexamples. A conspicuous star, a long list of palaces, or a dramatic transformation is not automatically the Main line. The goal is a conditional judgment that tells you what to test first.

The problem palace names the field, not the entire person. For a job question it may be Career, Wealth, Life, or Migration depending on whether the issue is role, resource conversion, agency, or external market. For a relationship question it may be Couple, Life, Ford, or Tianzhai depending on the task. A House combination is useful only after the domain is fixed; otherwise every connected palace can be made to sound relevant. Write the event, actors, decision, resource, and time window before interpreting the network.

Main stars describe ways a field may operate, while auxiliary and difficult stars can add access, friction, delay, visibility, support, or cost. Ask what each star does in this palace and what condition allows it to work. Do not count stars as votes for a Main line. A star may be central because it controls a resource, carries a responsibility, repeats through a transformation, or explains a bottleneck; it may be visually dramatic and still irrelevant to the question. Mechanism beats brightness.

Draw two or three candidate lines from the problem palace. For each, name the connected palaces, the direction of influence, the resource or responsibility that travels, and the practical fact it should explain. Three Parties and Four Uprightnesses can show support and carrying capacity; the opposite can show an external response or pressure; another palace can show the cost or receiving field. A line is stronger when the links form a coherent circuit rather than a pile of associations. Stop adding palaces when the question is already explained and extra links only add drama.

If the school uses Hua Lu, Hua Quan, Hua Ke, and Hua Ji, trace source star, transformation, destination palace, domain, and timing. A transformation may amplify a candidate line by repeating the same responsibility or attention route across relevant fields. Duplicate evidence means independent signals point to a similar mechanism; it does not mean repeating one phrase or counting the same star twice. Hua Lu does not prove benefit, Hua Quan does not prove control, Hua Ke does not prove approval, and Hua Ji does not prove failure. The flow strengthens a question for investigation, not a verdict.

The natal chart can show the recurring architecture of a problem, while a major or annual layer can make one candidate line active now. A line that explains a long-standing pattern may not be the line that explains this month’s decision. Compare natal structure, major cycle, annual trigger, and the actual sequence of events. Timing should narrow what to observe and when; it should not erase the distinction between a stable capacity, a temporary pressure, and a new opportunity.

Imagine a fictional chart and a practical question: why is a small clinic’s new outreach program exhausting its director? The problem palace is Career because the issue is role delivery. Candidate line A connects Career to Wealth and shows a budget-to-staffing bottleneck. Candidate line B connects Career to Migration and shows public visibility and new demand. Three Parties and Four Uprightnesses support both, but a major-cycle Hua Quan from Career reaches Wealth, while annual Hua Ke from Migration reaches Career. Duplicate evidence in the records shows unpaid coordination hours and repeated requests from new neighborhoods. The Main line for the immediate decision is A: authority and workload are not converted into staffing resources. The clinic limits the pilot, assigns a budget owner, records hours, and reviews demand before expanding publicity. B still matters for the next stage, but it does not explain the current exhaustion as directly.

A dramatic Migration star may attract attention because it describes a new audience, while the quiet Wealth line explains why the person cannot serve that audience. A repeated Four Transformation may look decisive but simply magnify a field already overloaded. Conversely, a subtle Life–Career connection may be the Main line when the real issue is agency and role boundaries. If two lines explain the same facts, prefer the one with fewer assumptions and clearer action. If they explain different layers, keep both but state which one answers which question.

Do not select a Main line because it has the most stars, the most auspicious or difficult labels, or the most complicated diagram. Do not treat an empty palace as no information, a Four Transformation as an automatic outcome, or duplicate evidence as permission to count one signal repeatedly. Do not let the Main line predict wealth, marriage, health, death, safety, promotion, or failure without a real mechanism and observable evidence. School rules and alternative interpretations must remain visible.

Record the question, problem palace, domain, actors, time window, candidate lines, House combination, Three Parties and Four Uprightnesses, opposite palace, stars, Four Transformations, duplicate evidence, natal and timing layers, proposed mechanism, supporting fact, counterexample, uncertainty, action, measurable result, stop condition, and review date. Test the selected line with a timeline, budget, workload log, conversation record, contract, experiment, or staged commitment. Re-rank the lines when reality contradicts the mechanism. Ziwei cannot replace medical, legal, financial, therapeutic, workplace, or emergency support and cannot guarantee wealth, relationship outcomes, health, safety, or success. A clear Main line should make a decision more testable, not make the future sound certain.