LJS 418, f. 3r, the remnants of a sewing repair with thread remaining
In parchment manuscripts one will often see small pin prick holes in the parchment which indicates that a hole in the animal skin was repaired during processing. Usually after curing and before use the thread from the repair is removed leaving only the small holes.
Rarely, but occasionally, the thread will still remain in the final manuscript. An example of this is LJS 418, f 3r where one can see the thread left in the page.
The smudged line indicating where the quire would have been originally folded is clear in the center of the folio.
Smudged or worn lines on manuscripts may be indicative of a manuscript having been unbound and potentially folded and possibly carried during regular use.
LJS 418 f. 6v shows an example of this pattern though the manuscript was later bound.
Mentioned at Coffee With a Codex on 2021-11-01 with an example on the closing pages of LJS 418, which isn't very clear/good, and another in MS Codex 1248, which is in a tiny manuscript, but very clear and lovely.
https://en.wikipedia.org/wiki/Blessed_salt_in_Christianity
Looked up in relation of mention of a blessing of salt and water in LJS 418, a manuscript about Saint Blaise: https://bibliophilly.library.upenn.edu/viewer.php?id=Oversize%20LJS%20418#page/12/mode/thumb