Rule 38 of 40 · Chapter VI — Tools, Habits, and Judgement
Label what you leave behind
Why this rule exists
The next person to open that panel might be a stranger, or you in five years having forgotten everything. Clear labels, accurate directories, tagged conductors, marked disconnects, are how your knowledge survives to protect whoever works the system next. An unlabeled or wrongly labeled panel sends someone to work a circuit they believe is dead. Good labeling is a safety device with no moving parts: it prevents the mistake before anyone can make it. You are not just finishing a job; you are leaving a map for whoever inherits it.
In practice
Update the circuit directory with specific, legible descriptions whenever you change anything. Label multiwire branch circuits and shared neutrals so the next person does not open a neutral under load. Mark disconnects with what they control. Tag unusual arrangements, junction boxes, and anything not obvious. Leave documentation, a photo, a note in the panel, for complex work. Use durable labels that survive the environment. When you find bad labeling, fix it rather than working around it; you may be the last person who knows the truth of that circuit.
When it doesn't apply
Labels must be accurate to help; a confidently wrong label is worse than a blank one, because it invites trust. Verify before you label, and re-verify labels you inherit rather than trusting them blindly; the directory is a guide, the tester is the proof. Some identification requirements (conductor colors, disconnect marking) are code-mandated, not optional; meet those as the minimum.