VOUSSOIR (Ger. Wolbeslein), the French term used by architects for the wedge-shaped stones or other material with which the arch (q.v.) is constructed; the lowest stone on each side is termed, the springer (Fr. coussinet sommier) and the upper one at the crown of the arch the keystone (Fr. daveau).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)