About Box Drawing Symbols
These twenty-four characters come from the character sets of early PC terminals, where they were used to draw boxes, tables, and menu frames on screens that could only display text. They were designed to interlock — the right edge of ─ meets the left edge of ┬ exactly — and that design assumption is the single most important thing to know before using them.
They Only Line Up in a Monospaced Font
Interlocking requires every character to occupy exactly the same width. That is true in a terminal, in a code block, and in any monospaced font. It is not true in the proportional fonts used by essentially every social media bio, chat app, and profile page.
In a proportional font the line segments end up at different widths and the frame comes apart — corners that do not meet edges, horizontal runs that do not align with the box above them. Nothing is broken; the characters simply are not being given the equal widths they assume.
This is why box drawing works beautifully in a Discord code block or a README and disappointingly in an Instagram bio. If the destination does not use a monospaced font, a single repeated character like ▬ is a more reliable rule than a constructed frame.
Single, Double, and Solid
There are three families here. ─ │ ┌ ┐ └ ┘ ├ ┤ ┬ ┴ ┼ are the single-line set. ═ ║ ╔ ╗ ╚ ╝ ╠ ╣ ╦ ╩ ╬ are the double-line equivalents, each a direct counterpart of a single-line character.
The families are complete within themselves and should not be mixed — a double-line corner will not meet a single-line edge, because they were never designed to. Pick one family per frame.
▬ and ▭ are different in kind: a solid black rectangle and a hollow one, both useful as standalone rules or bullets rather than as parts of a frame.
Where They Work Well
Discord and similar chat apps render code blocks in a monospaced font, which is where these characters do exactly what they were designed to do. The same applies to plain-text files, terminal output, and documentation.
All twenty-four are plain text characters with excellent font coverage, and they take the colour and weight of the surrounding text. For decoration that does not depend on alignment, the decorative symbols are the better fit, and the shape symbols cover filled and hollow blocks.