JAMB (from Fr. jambe, leg), in architecture, the side-post or lining of a doorway or other aperture. The jambs of a window outside the frame are called " reveals." Small shafts to doors and windows with caps and bases are known as " jamb-shafts "; when in the inside arris of the jamb of a window they are sometimes called " scoinsons."
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)