A line like
Field3=any text here
in the index file associates the text "any text here" with user defined field 3. The '3' in this example can be replaced with any number from 0 to 19. A fielded search is invoked by a URL like
<http://host/dir/search=field3>
In addition to fielded searches the user supplied fields can be inserted in documents. This is done by including the marker <!-- #WN_field3 --> in the file at the point where the value should be inserted. This should occur on a line by itself with no whitespace before it. If there is no Wrappers= or Includes= line in the index file for this entry then there must be a line like
Parse=true
so the server knows it is to parse the file to look for the marker.