The Triple Vertical Bar Right Turnstile symbol (⊪). Copy and paste it, or use its Unicode, HTML, and CSS codes.
More from Math.
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+22AA (decimal 8874).
Use ⊪ in HTML to render ⊪ on a web page.
On Windows you can type it with Alt+8874 (hold Alt and enter the number on the numeric keypad).
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