diff --git a/tren.rst b/tren.rst
index 245fb68..75dada6 100644
--- a/tren.rst
+++ b/tren.rst
@@ -897,6 +897,61 @@
 invocation.
 
 
+Limiting Renaming To Only Part Of Name
+======================================
+
+Sometimes you just want to rename a *part* of a file- or directory
+name (aka a name "substring").  As described below, you can use a
+Regular Expression to do this, but this can be complicated and is
+often overkill for simple substitutions.  **tren** gives you the
+ability to limit the renaming action to a "targeted" portion of the
+name using the ``-T`` option.  You simply supply a "slice" describing
+the portion of the name to be renamed::
+
+  tren.py -i: -T :3  -r=x  abcdef.text # -> xdef.text
+  tren.py -i: -T :-4 -re=E abcdef.text # -> abcdEf.text
+
+It's important to understand how ``-i`` and ``-T`` interact.  Even
+though all instances of a matching old string are specified via the
+``-i:`` option, the ``-T`` option that follows it limits the portion
+of the name being considered for renaming.  For instance, in the
+second example, removing the ``-T`` targeting gives us::
+
+  tren.py -i: -re=E abcdef.text # -> abcdEf.tExt
+  
+In summary, ``-T`` defines what substring of the full name
+is a candidate for renaming.  All other renaming operations
+like ``-i``, ``-r``, and so on operate *only upon the substring
+specified by* ``-T``.
+
+
+More About Slice Notation
+=========================
+
+Both the ``-i`` and ``-T`` options use "slice" notation so
+it's useful to understand a bit more about how "slices" are
+constructed.
+
+.. NOTE:: Although both options use slice notation, they mean very
+          different things.  In the case of ``-i``, the slice specifies
+          which *instances* of an old string are to be replaced.
+          In the case of ``-T``, the slice defines which *characters*
+          in the original file name are "targeted" for renaming.
+
+**tren** is written in the Python programing language.  The slice
+notation is lifted directly from that language.  if you're a Python
+programmer, you can skip this section :)
+
+Imagine you have a filename like this::
+
+  abcdef.txt
+
+
+
+
+
+
+
 Multiple Substitutions
 ======================
 
@@ -2896,7 +2951,7 @@
 
 ::
 
-  $Id: tren.rst,v 1.193 2010/09/08 19:50:16 tundra Exp $
+  $Id: tren.rst,v 1.194 2010/10/18 19:06:29 tundra Exp $
 
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