繕

A phono-semantic compound composed of:

糸 — semantic component meaning “thread; textile,” indicating actions like sewing or repairing;

善 — phonetic component indicating the sound (선 / shàn).

The meaning developed from the idea of using thread to fix something, thus repairing or improving it (i.e., making it “good,” as suggested by 善).
Semantic development: - to sew or mend with thread; - to repair or fix; - to restore something to a good condition.

수선 (修繕) — repair; maintenance

보선 (補繕) — repair; patching

The character emphasizes restoring something to a proper or good state, not just fixing damage. It is commonly used in formal contexts such as building maintenance, document preparation, or restoration work.
Related characters: 修 — to repair; to fix

補 — to mend; to patch

善 — good; virtuous