arrow bitmaps.
If value is a symbol `left' or `right', both angle and arrow bitmaps
-are displayed in the left or right fringe, resp.
+are displayed in the left or right fringe, resp. Any other value
+that doesn't look like an alist means displat the angle bitmaps in
+the left fringe but no arrows.
-If value is an alist, each element (INDICATOR . POSITION) specifies
-the position of one of the indicators. INDICATOR is one of `top',
+You can exercise more precise control by using an alist as the
+value. Each alist element (INDICATOR . POSITION) specifies
+where to show one of the indicators. INDICATOR is one of `top',
`bottom', `up', `down', or t, which specifies the default position,
and POSITION is one of `left', `right', or nil, meaning do not show
this indicator.