Intended as the presentation from a diplomatic point of view of a celebrated manuscript, the Libro del chiodo, housed in the Florentine State Archives and recently published in a critical edition with facsimile, the essay underscores the characteristics and importance of the work executed around the mid-14th century by the notary to whom we owe the collection of the various documents contained in the manuscript. Recorded in this manuscript are the condemnations made by the Florentine Guelph party to its opponents, the Ghibellines and the White Guelphs, including lists of their names, among whom Dante Alighieri, exiled and sentenced to death in 1302. Various compilations of more or less the same time period contain in part or in full the documents of the Libro del chiodo, a manuscript that is distinguished from these other testimonies in that it has survived in its entirety and that it was written by a noted professional, not associated with the Guelph party, on the basis of the acts of the Riformagioni archive, and not using sources with factional leanings. Its authority, also derived from the particular structure of the text and its various parts, is further confirmed by the fact that only a few years after its redaction, the Libro del chiodo became the official book of the Guelph party within which all of the condemnations inflicted on political enemies of the mercantile oligarchy had to be registered.