When a client stops talking to you, your instinct says to send another message, and that is exactly pushing on the corner that broke. The booklet's rule runs the other way: to raise one corner of a relationship you use the other two, and you start from what both sides already agree on.
The rule as the source puts it
The booklet takes this rule from a policy letter. A relationship between people is a triangle of affinity (how much the two like each other), reality (what they agree on) and communication (what passes between them). Of the three, communication is the most vital. And when you want to raise one corner of the triangle, you use the other two.
The source spells it out. If you want more communication, raise affinity and reality. If you want more reality, raise affinity and communication. If you want more affinity, raise reality and communication.
It sounds like wordplay, but it follows from the earlier chapters of the booklet. The three corners depend on each other, so a corner that was cut comes back through the two that still hold it.
Why it runs against instinct
The client went quiet, and the natural reaction is to write him more, and then a little more. In the booklet's terms that is pushing directly on the cut corner, and the rule says to leave it alone for a moment and work on the other two.
There is a plain reason. The booklet's first chapter says communication exists to be answered, and a message that got no reply has failed at its job. Every extra message sent to a cut corner is one more attempt that fails, and when that repeats with the same person, even the sender stops in the end.
Suppose a client who stopped replying. Instead of another message asking for an answer, the owner sends an offer the client is certain to accept, such as moving the job to next month at no cost. That agreement opens the door to communication again.
Or a partner who disagrees with you on almost everything. Instead of another argument on the same subject, first comes an action that raises affinity between you, and only after it the conversation. It is the same subject on different ground.
Without agreement the message does not land
Here is why this works. According to the source, communication is the most important of the three, yet when there is no reality, no agreement of any kind, it will never reach its target, and affinity will be missing too.
So the importance of communication is exactly the reason you cannot push it alone. It needs something to stand on, and agreement supplies that.
This explains why a correct, well-argued message can fall on deaf ears. Its wording was fine. What it lacked was a base of agreement, so it had nothing to land on.
Suppose a detailed email about a price rise, well reasoned, that got a one-word reply. The email itself was fine. What was missing was an earlier agreement that prices were meant to change at all.
The reverse case: an owner who had agreed with the team beforehand that prices get reviewed every quarter. When the next price went up, it was a familiar routine and no surprise.
What is agreed comes first, the rest after
The source gives the rule a practical form. You find the point the other side already agrees with and lean on it, and from there you have a shared reality, an agreement, and they will listen.
This connects to the definition the booklet gives reality in chapter 4: reality is basically agreement. When you open on what is agreed, you build a shared reality first, and only on it do you ask the other side to listen to something new.
In business language, that means opening on what is agreed and leaving the contested point for later. The source adds a broader rule: when you improve one corner of the triangle, you improve the other two as well.
Suppose a conversation with a supplier about late deliveries that opened with the fact that both of them want the owner's client to stop phoning the supplier directly. Full agreement from the first second, and the talk about timings that followed was easy.
The reverse case: the very same conversation, opened by accusing the supplier of being late all the time. Half an hour of defence, and nothing changed.
The booklet describes this agreement as ground, the place where you can stand what is not yet agreed. Whoever opens with it gives nothing up.
What the booklet adds
This chapter of the booklet comes with two exercises: a build exercise and an analysis exercise. In the chapter after it, the booklet explains how to adjust the tone you use to the state the other side is in, so you stop talking over their head.
When a message does not land, sometimes what it lacks is a ground of agreement to land on, and better phrasing would not have helped.
The booklet is general knowledge about communication, not legal advice for a business dispute. The repair also depends on the other side.