/sys$common/syshlp/helplib.hlb INSTALL, ADD, Qualifiers, /WRITABLE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /WRITABLE
       /NOWRITABLE

    Installs the file as a writable known image as long as you also
    specify the /SHARED qualifier. The /WRITABLE qualifier only
    applies to images with image sections that are shareable and
    writable. The /WRITABLE qualifier is automatically negated if the
    /NOSHARED qualifier is specified.