/sys$common/syshlp/helplib.hlb FORTRAN, Format Specifiers, H  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  nHc1c2c2...cn (Hollerith Editing)

  On input, transfers "n" characters from the external record to the
  field descriptor itself.  The first character appears immediately
  after the H.  Any characters in the field descriptor before the
  input operation are replaced by the input characters.

  On output, transfers "n" characters following the letter H from the
  field descriptor to the external field.