diff --git a/tbku.txt b/tbku.txt
index 452c393..716ffcb 100644
--- a/tbku.txt
+++ b/tbku.txt
@@ -81,9 +81,49 @@
 or file specified in the $TAPEDEV variable instead of a file in the
 backup directory.
 
-**CUSTOMIZING**
+**CUSTOMIZING tbku**
 
-  'tbku'
+  ``tbku`` is written to be "smart" enough to figure out where your
+  system keeps needed tools like ``tar`` or ``sed``.  The only
+  requirement here is that ``tbku`` be run in an environment that can
+  find the ``which`` command somewhere in its ``$PATH`` - ``tbku``
+  uses ``which`` to figure out just where everything it needs lives on
+  your filesystem.  If ``tbku`` cannot figure out where your system
+  keeps things, it will use the FreeBSD default values.
+
+  For most FreeBSD and Linux users, this should work without any
+  customization beyond setting environment variables to override
+  default behavior (described below).  In rare circumstances, you may
+  need further customization.  All the things you're likely to ever
+  want to change appear first in the actual ``tbku`` script, and are
+  briefly documented there.
+
+
+**ENVIRONMENT VARIABLES & DEFAULTS**
+
+  You can override the various ``tbku`` defaults by setting a
+  corresponding environment variable.
+  
+
+  =================  ===============================  ======================
+  **Env. Variable**  **Default Value**                **Meaning**
+  -----------------  -------------------------------  ----------------------
+  TBKUDIR            /bku                             Where to write backups
+  TBKUNAME           $MACHINE-$OSTYPE-$OSREV-$HWTYPE  Tarball base name
+  TBKUSETS           $HOME/tbku                       Filesets found here
+  TBKUTAPE           /dev/sa0                         Tape device (or file)
+  =================  ===============================  ======================
+
+
+  Examples::
+
+    export TBKUDIR=/mnt/backups    # Backups written to /mnt/backups
+
+    export TBKUNAME=JoeBackup      # Backups named: JoeBackup-<filesetname>
+
+    export TBKUSETS=/tbku          # Looks for filesets in /tbku
+
+    export TBKUTAPE-/tmp/faketape  # Tape backups actually written to *file*
 
 
 **UPDATES & SUPPORT**
@@ -121,4 +161,4 @@
 
     http://docutils.sourceforge.net/rst.html
 
-``$Id: tbku.txt,v 1.104 2008/03/19 15:23:48 tundra Exp $``
+``$Id: tbku.txt,v 1.105 2008/03/19 16:31:36 tundra Exp $``