What ⇠ means
The dashes alter the line, not the direction. A diagram may assign dashed lines a convention of its own, so read ⇠ within the notation around it.
Don't confuse it with
4Questions people ask
1Why does ⇠ show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type ⇠
Windows (Word)
Alt+XType 21E0, then Alt+X to get ⇠.
Windows
Win+Rrun charmap for the full table, or use the emoji picker's Ω symbols tab (Win + .).
macOS
Control+Command+SpaceOpen the character viewer and search “leftwards dashed arrow”.
Linux
Ctrl+Shift+UType 21e0, then Enter or Space.
HTML
⇠CSS
\21E0Codes and encoding1 code points
HTML decimal
⇠
HTML hex
⇠
CSS content
content: "\21E0";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%87%A0
1
On screen
1
Code points
1
JS .length
3
UTF-8 bytes
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.