The Shouldered Open Box symbol (⍽). Copy and paste it, or use its Unicode, HTML, and CSS codes.
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The quickest way is to copy ⍽ from this page and paste it anywhere. You can also insert it with its Unicode, HTML, or alt code listed above.
⍽ is U+237D (decimal 9085).
Use ⍽ in HTML to render ⍽ on a web page.
On Windows you can type it with Alt+9085 (hold Alt and enter the number on the numeric keypad).
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