In a conference on New Directions in Medieval Manuscript Studies, the newer developments in codicology ought to be represented. I regret that no speaker was found for Quantitative Codicology; but at least some quite technical aspects can be discussed. And although these matters are often of scant relevance for those scholars – surely the vast majority – who study medieval manuscripts for the sake of their texts, still they have their interest as part of the history of a craft; and from time to time they are relevant to text scholars as well.

I

Everybody knows what folio, quarto and octavo are. In the bibliography of the printed book these terms denote the format, that is: they indicate (in principle) that during printing two, four or eight leaves were attached, and that these constituted a whole sheet as produced by the paper mill. There is an advantage, especially for studying manuscript books, in distinguishing several aspects of format: first the question what part the leaf, as we see it in the book, was of the sheet as produced by the supplier (what I call the material format); and then the further question what leaves, if any, had been still attached during the production of the book. Actually, of course, one should ask these questions not about leaves but about bifolia, which are the real constituents of the book.