It's a clever trick actually, though it doesn't compose the way the traditional box-drawing characters do. Good for one (1) box, where you want to be able to set the background without bleed.
A 1-dimensional, 1-sided horizontal example would be if you have abcdef in the background partially covered by ABCDEF in the foreground. With a vertical bar in the middle, it looks like
abc|ABCDEF
abc |ABCDEF