... at the front of their workbenches, which is made of one piece of wood n n, figure 3 and 4, which is 4” to 5” wide by at least 2” thick.
This piece is pierced in the middle of its width by a round hole through which passes the screw o p, to which the workbench leg q serves as its nut.
This screw is usually wood and through its head passes an iron bolt r, with which tightens and loosens the screw. We adorn the head of the screw with an iron ring to prevent it from splitting.
The use of these vises is very convenient because not only do the vises hold the work very solidly, but they do not mar the work in any way. No matter how delicate the pieces are, we do not fear to ruin them. This is something we can’t do with a leg holdfast, which is holding the work only in one place and will sometimes break it if it is delicate.
-from "L’Art Du Menuisier". Trans. Bjenk Ellefsen. Courtesy of Lost Art Press