(Fr. rein), the term given in architecture to the stone from which an arch springs (see Arch); in some cases this is the stone resting on the impost or capital, the u p per surface of which is a plane directed to the centre of the arch. In vaulting, however, where the lower stone of the arch or rib is laid in horizontal courses, so as to bond it well into the wall, constituting a system of construction known in France as the tas-de-charge, the springer may be considerably higher. The term is sometimes applied to the lowest stone of a gable.