July 24, 1965
A wedge-shaped stone placed at the apex of a masonry arch is called a keystone. During construction of the arch, the keystone is the final piece to be placed.
They used a keystone. It is a wedge-shaped piece at the top of an arch. It is the final piece placed to lock in the other stones of the arch.
Gateway to the West. jkernan
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The key stone is the stone placed at the apex of the arch, and prevents the two sides of the arch falling in and collapsing.
A keystone. PA was named the Keystone state as it was in the middle of the 13 colonies, much like a keystone in an arch or doorway. It's the stone at the top, middle of the arch which holds the arch in place. If the keystone is removed, the arch topples.
The Gateway arch is in St Louis, Missouri
To hold the arch in place
Because it IS an arch.
the gateway arch
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Edication