(Chapter 39) Footnote 33:

A marginal note refers the reader to items in the illustration at the beginning of Bk. 2, ch. 7: S (coils of brass wire), T (an awl), V (an assortment of drill bits), X (a pair of pincers for twisting the ends of wires), and Y (another kind of pincers for cutting off twisted wires). So, at least, they are labeled there, but it appears that the identifications of X and Y have been reversed as X is the nipper and Y has flat, square jaws. The 1555 edition adds an insert illustration and a description [see Appendix] of a drill powered by a bow and string.