Variable: display-fill-column-indicator-character

display-fill-column-indicator-character is a customizable and buffer-local variable defined in xdisp.c.

Documentation

Character to draw the indicator when display-fill-column-indicator is non-nil.

A good candidate is U+2502, and an alternative is (ascii 124) if the font of fill-column-indicator face does not support Unicode characters. See Info node (emacs)Displaying Boundaries for details.

This variable was added, or its default value changed, in Emacs 27.1.

Probably introduced at or before Emacs version 27.1.

Source Code

// Defined in /usr/src/emacs/src/xdisp.c
  DEFVAR_LISP ("display-fill-column-indicator-character", Vdisplay_fill_column_indicator_character,
    doc: /* Character to draw the indicator when `display-fill-column-indicator' is non-nil.
A good candidate is U+2502, and an alternative is (ascii 124) if the
font of `fill-column-indicator' face does not support Unicode characters.
See Info node `Displaying Boundaries' for details.  */);