+lines. A thread could be drawn like this:
+
+@example
+>
++->
+| +->
+| | \->
+| | \->
+| \->
++->
+\->
+@end example
+
+You can customize the appearance with the following options. Note
+that it is possible to make the thread display look really neat by
+replacing the default ASCII characters with graphic line-drawing
+glyphs.
+@table @code
+@item gnus-sum-thread-tree-root
+@vindex gnus-sum-thread-tree-root
+Used for the root of a thread. If @code{nil}, use subject
+instead. The default is @samp{> }.
+
+@item gnus-sum-thread-tree-single-indent
+@vindex gnus-sum-thread-tree-single-indent
+Used for a thread with just one message. If @code{nil}, use subject
+instead. The default is @samp{}.
+
+@item gnus-sum-thread-tree-vertical
+@vindex gnus-sum-thread-tree-vertical
+Used for drawing a vertical line. The default is @samp{| }.
+
+@item gnus-sum-thread-tree-indent
+@vindex gnus-sum-thread-tree-indent
+Used for indenting. The default is @samp{ }.
+
+@item gnus-sum-thread-tree-leaf-with-other
+@vindex gnus-sum-thread-tree-leaf-with-other
+Used for a leaf with brothers. The default is @samp{+-> }.
+
+@item gnus-sum-thread-tree-single-leaf
+@vindex gnus-sum-thread-tree-single-leaf
+Used for a leaf without brothers. The default is @samp{\-> }
+
+@end table
+