squinch

thumb|250px|Squinches supporting a dome in Odzun Basilica, Armenia, early 8th century

In architecture, a squinch is a structural element used to support the base of a circular or octagonal dome that surmounts a square-plan chamber. Squinches are placed to diagonally span each of the upper internal corners (vertices) where the walls meet. Constructed from masonry, they have several forms, including a graduated series of stepped arches; a hollow, open half-cone (like half of a funnel laid horizontally, also called a trumpet arch); or a small half-dome niche. They are designed to evenly spread the load of a dome across the intersecting walls on which it rests, thus avoiding concentrating higher structural stress on smaller load-bearing areas. By bridging corners, they also visually transition an angular space to a round or near-circular zone.