☇

#90 degree #arrow #90 degree arrow

🔺∟

#right triangle #right angle symbol #90 degree #angle symbol

🔺⬜

#right triangle #90 degree #square corner

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#angle symbol #90 degree #perpendicular

🪵📐∟

#woodworking #joinery #carpentry #mitre joint #angle cut #corner joint #45 degree #90 degree