DIAMOND, in the glass-trade, an instrument used for squaring the large plates or pieces; and, among glaziers, for cutting their glass.
These sort of diamonds are differently fitted up; that used for large pieces, as looking-glasses, &c. is set in an iron ferril, about two inches long, and a quarter of an inch in diameter; the cavity of the ferril being filled up with lead, to keep the diamond firm: there is also a handle of box, or ebony, fitted to the ferril, for holding it by.