When you create an Access Control Entry (ACE) for a di-
  rectory, DECdns automatically copies (propagates) the ACE
  into the Access Control Sets (ACSs) of all the child directo-
  ries you may later create under that directory.  Note that
  P-flagged ACEs are not inherited by anything other than fu-
  ture child directories.  However, default ACSs are inherited by
  nondirectories.  Automatic propagation of every ACE that you
  create for a directory always occurs unless you set the P flag
  to off (after you unlock the ACS, click once on the P flag to
  turn it off).

  You should turn the P flag off when you want to create an
  ACE for a directory, but would prefer that the rights you
  grant be applied only to that particular directory and not be
  inherited by any future child directories.