Question

when the topmost block on a round arch, called the ______, is wedged into place, the two sides of the arch meet and lean against each other.

multiple choice
buttress
keystone
dome
oculus
corbel

Explanation:

Identify the architectural element

Using the Architectural Terminology knowledge point

The question asks for the name of the topmost block on a round arch that, when wedged into place, locks the two sides of the arch together so they lean against each other.

• Keystone: The wedge-shaped stone piece at the apex (topmost point) of a round arch. It is the final piece placed during construction and locks all the other stones (voussoirs) in place, allowing the arch to bear weight.
• Buttress: An exterior support built against a wall to counteract the outward lateral thrust of an arch or vault.
• Dome: A rounded vault forming the roof of a building or structure, typically with a circular base.
• Oculus: A circular opening at the center of a dome or in a wall.
• Corbel: A structural piece of stone, wood, or metal jutting from a wall to carry a superincumbent weight.

Therefore, the correct term is the keystone.

Answer:

• buttress
• keystone (Correct answer)
• dome
• oculus
• corbel