in architecture is 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 corbelled
courses, by filling the corner with a vise
placed diagonally, or by building an arch or a number of corbelled 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 corbelled stalactite-like structures known as muqarnas. It was also commonly used in the early churches of Europe and the East.