Combining Double Vertical Line Below

Combining Double Vertical Line Below at U+0348 is a nonspacing diacritic that adds a pair of short vertical strokes underneath the preceding character. It belongs to the Combining Diacritical Marks block and is meant to modify a base letter or symbol rather than appear on its own. Its practical use is highly specialized. It is mainly found in phonetic, phonological, and scholarly transcription systems that need a below-letter mark not already covered by more common diacritics, especially in custom notations for linguistic fieldwork, dictionary projects, or editions of minority-language data. Because it combines with the character before it, the visual result depends on the base letter and the font’s mark positioning. The main gotcha is that it can be easy to miss in plain text: searches, cursor movement, and deletion may treat the base character and the below mark as separate code points even though they look like one annotated letter.