Literal translation
to make a sardine
Meaning
to make a crease or fold badly
Explanation
Names a crease left by mistake, in fabric while ironing or in wallpaper while gluing it. The sardine, an emblematic Mediterranean fish, lends its shape to the offending fold, reinforced by a related Provençal image : a sardine curls up when grilled, hence the phrase indignant as a cooked sardine. A stray crease, precisely, is a disgrace.