only use the centrally provided (and vetted) master file (which is
automatically updated when you run the PCTB client, by default).
+It is also possible to have the OCR system reject particular strings.
+If you put a regexp in #local-reject#.txt, any OCR result which
+matches this string will instead cause an OCR failure, invoking the
+OCR dictionary editor if appropriate. #master-reject#.txt is the
+centrally maintained version of this file.
+
Alternatively you can edit #local-char15#.txt with a text editor. The
format is not documented at the moment.