@kbd{C-x 3} (@code{split-window-horizontally}) breaks the selected
window into two side-by-side windows. A numeric argument specifies how
many columns to give the one on the left. If you are not using
-scrollbars, a line of vertical bars separates the two windows.
+scrollbars, a vertical line separates the two windows.
+You can customize its color with the face @code{vertical-border}.
Windows that are not the full width of the screen have mode lines, but
they are truncated. On terminals where Emacs does not support
highlighting, truncated mode lines sometimes do not appear in inverse