What does it mean that boundaries require communication?

People cannot respect boundaries they do not know exist.

Example: You resent your colleague for calling you at 9 PM about non-urgent issues. You have never told them you don't take work calls after 7 PM. In your head, this boundary is obvious — you have a family, evenings are sacred, everyone should know this. But they don't know. They call because nothing in your shared reality has marked that time as off-limits. Your resentment is real, but it is aimed at someone who violated a rule they were never given.

Try this: Identify one boundary you currently hold only in your head — something you expect others to respect but have never explicitly stated. Write it down in the format: 'I need [specific boundary]. The person who needs to hear this is [name]. I have not communicated it because [reason].' Then draft the actual statement you would use to communicate it. Do not send it yet. Just notice the gap between how obvious the boundary feels to you and how invisible it is to the other person.