Definition
Rag
The rag is the uneven edge of unjustified text — the right edge in left-aligned setting. A good rag is shallow and irregular; a bad one forms shapes, wedges or near-straight runs.
Editing the rag is the quiet craft of unjustified setting. Typesetters look for three faults: a line ending far shorter than its neighbours, several lines ending at almost the same point so the edge looks accidentally justified, and a hyphen or short word stranded alone. The repair is usually a small tracking change or a manual break, not a change of alignment.
Related tools & guides
See it handled in your own manuscript
Ceeryo sets your .docx as a book — justified and hyphenated text with widows, orphans and rivers controlled, drop caps, running heads — and shows you every spread before you pay anything.