Structural arches have been assembled out of individual wedge-shaped stones known as voussoirs, with the last and topmost one to be put into place called the keystone for millennia. Placing the keystone in a true arch presented a special problem, for unlike all the other pieces of stone in an arch, it could not be. lifted approximately into place atop the centering and then pushed and shoved more or less easily into its proper place and orientation. The keystone had to be dropped directly into the gap left between the two halves of the incomplete arch, with any sideways adjustment done before the final placement. The central functional and symbolic nature of keystones has led to their esthetic elaboration and exaggeration in structures employing the arch and vault, the latter of which can be thought of as a continuous series of side-by-side arches.
Volume / Issue
Start / End Page
International Standard Serial Number (ISSN)
Digital Object Identifier (DOI)