squinch, in architecture, a piece of construction used for filling in the upper angles of a square room so as to form a proper base to receive an octagonal or spherical dome. It was the primitive solution of this problem, the perfected one being eventually provided by the pendentive. Squinches may be formed by masonry built out from the angle in corbeled courses, by filling the corner with a vise placed diagonally, or by building an arch or a number of corbeled arches diagonally across the corner. In Islamic architecture, especially in Persia, where it may have been invented, the squinch took the form of a succession of corbeled stalactites. It was also commonly used in the early churches of Europe and the East.