What is a Keystone?

What is a keystone? You might think that all arches are made the same way. The fact is they are not all the same. Typical Roman arch with keystone. It is true that Egyptian, Babylonian, Greek and Assyrian civilizations used arches for underground structures such as drains and vaults. However, it was the Roman civilization (1000 B.C.E. - 500 C.E.) that first began using a keystone (also called a capstone) in their arches. The keystone is the topmost stone in the arch. The one in the illustration on the right is exaggerated in size from what a normal keystone would be.

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PA Department of Labor & Industry on X: Having trouble creating your Keystone ID? Here are some tips that may help you troubleshoot issues you may be having. / X

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Schematic diagram of the keystone process concept. In an arch, a

Article - What Is A Keystone Species, PDF, Ecology

The keystone metaphor. The keystone is the component of a structure