Dear Péter-Dániel, I'm not sure what your question is.  However, this whole issue about book production is under-explored and very interesting, so it's a great topic to raise.

If you're talking about paper MSS, one point I could mention: you refer to horizontal lining.  Do you mean written lines, or indentations in the paper?  I have seen - and you have too, I expect - wooden boards that are shaped the same a s a paper folio, with holes left and right for stretching six to ten lines of string horizontally.  The paper of a leaf was pressed to this string-board (rajjuphalaka*?  sūtraphalaka*?) and the impression of strings formed the guide-lines for scribes.  So one finds paper manuscripts with these faint concertina-like indentations on them, that were evidently made with such a tool.

In European codicology, a manuscript atelier in a monastery would have a wheel with pins sticking out of the rim, like extended spokes.  What LW Jones called "a sharp awl" (p. 392)  It was run down each side of the manuscript leaf, forming an eye-line between the pinpricks, so the scribes could write in straight lines.  These so-called manuscript prickings have been used by codicologists to identify particular pricking-awls, and therefore to identify the monastery in which a particular codex was written.  

I've often wondered whether the Indian string-boards could offer a similar guide, but I think probably not.  The reasons are that there are too many of these boards.  One often finds them kicking around with a pile of manuscripts.  I think scribes probably made them quite frequently, for ad hoc use.  Secondly, Indian codicology is still in its infancy, and since most Indian manuscript catalogues omit any serious physical description, one would have to study original collections on a wide scale to get any kind of grip on this feature.

Best,

Dominik

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