Where is the vertical-border char set?

[Trent W. Buck]

Stupidly, I started doing this today:

    (setq mode-line-end-spaces (make-string 1024 ?─))

It makes the modeline look prettier (except when it doesn't).
The 1024 is arbitrary, it replaces %- (infinite MINUS HYPHEN).
I can't see how to ask for infinity of an arbitrary codepoint.

I want to do the same thing for the vertical-border character,
which is "|" for me (my window-system is nil).

Where do I set that?
CAN I set that?
I tried apropos-variable and apropos-value and grepping lisp/ and src/,
but my fu is weak.