Visorum

Some compositors use visorums. Therefore pricking the point of the visorum, most commonly upon the border or frame of the case on the left hand about the & box, they fold the leaf of copy they compose by, so as the bottom of it may rest upon the square shoulder near the bottom of the visorum; then with two pieces of scaleboard tied together at one end, they clasp both the copy and visorum between these two scaleboards, which two scaleboards pinch the copy and visorum fast enough to keep the copy in its place, and at the same time also serves for an index to direct the eye to every line, as the compositor moves it downward. — M.

This article is not used now; though it appears to me, from Moxon's account, to be both useful and convenient.