Every chart carries a legend because symbols mean nothing until they are keyed. A character card needs the same courtesy — not for visitors, but for its own maker, three months from now, reading lines that felt unforgettable when they were written and are merely ambiguous today.
The legend habit is simple: every term on the card must be checkable in a frame. If a line says her hair is “waved”, the legend in your notes says what waved means here — over one shoulder, past the shoulder blade, never curled. If the signature is a small mark, the legend says where it sits, so a crop can be checked honestly instead of generously.
Write the legend when the card is written, in the same sitting, while the decisions are still warm. It takes ten minutes, and it is the difference between a card that holds a character for a season and a card that holds her for a week.
Charts outlive their makers’ memories. Legends are how. Keep both, and the atlas stays true long after the first sitting is forgotten.