mathematics - What's the word for the small square indicating a right angle in a geometric figure? - English Language & Usage Stack Exchange

I'm talking about something in geometry notation and/or drafting, I think. It's the mini right-angle shape you can draw within an angle to indicate that it's ninety degrees. E.g., the mark denoting

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mathematics - What's the word for the small square indicating a right angle in a geometric figure? - English Language & Usage Stack Exchange

Sage Academic Books - Mathematics Formative Assessment, Volume 2: 50 More Practical Strategies for Linking Assessment, Instruction, and Learning