Keystone

Definition

The keystone is the central wedge-shaped stone at the topmost part of an archway. It is crucial for maintaining the stability and integrity of the arch, as it locks all the other stones in place.

Related terms

Voussoirs:

The wedge-shaped stones that surround the keystone and make up an arch.

Springing Point: The point where an arch begins to curve upwards from its supporting structure.

Arch Ring: The complete circular or semi-circular arrangement of voussoirs and keystones that form an arch.