+ (outside-staff-placement-directive ,symbol? "One of four directives
+telling how outside staff objects should be placed.
+@itemize @bullet
+@item
+@code{left-to-right-greedy} -- Place each successive grob from left to
+right.
+@item
+@code{left-to-right-polite} -- Place a grob from left to right only if
+it does not potentially overlap with another grob that has been placed
+on a pass through a grob array. If there is overlap, do another pass to
+determine placement.
+@item
+@code{right-to-left-greedy} -- Same as @code{left-to-right-greedy}, but
+from right to left.
+@item
+@code{right-to-left-polite} -- Same as @code{left-to-right-polite}, but
+from right to left.
+@end itemize")