KEYSTONE

Keystone

A keystone is the wedge-shaped stone piece at the apex of a masonry vault or arch, which is the final piece placed during construction and locks all the stones into position, allowing the arch to bear weight. Although a masonry arch or vault cannot be self-supporting until the keystone is placed, the keystone experiences the least stress of any of the voussoirs, due to its position at the apex. Old keystones can decay due to vibration, a condition known as bald arch.

The above text is a snippet from Wikipedia: Keystone (architecture)
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keystone

Noun

  1. The top stone of an arch.
  2. A native or resident of the American state of Pennsylvania.


The above text is a snippet from Wiktionary: keystone
and as such is available under the Creative Commons Attribution/Share-Alike License.

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