The Apl Functional Symbol Quad symbol (⎕). Copy and paste it, or use its Unicode, HTML, and CSS codes.
More from Tech Symbols.
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+2395 (decimal 9109).
Use ⎕ in HTML to render ⎕ on a web page.
On Windows you can type it with Alt+9109 (hold Alt and enter the number on the numeric keypad).
Yes — copying is completely free and unlimited, and works right in your browser with no sign-up.