The Selector is implemented as a Fortran subroutine library containing general tasks for manipulating FITS format files. All access to the FITS files is performed through the FITSIO library. The Fortran subroutine library is the basis of a set of FITS file manipulation tasks which we call FTOOLS (these are analogous to the STSDAS TTOOLS tasks). These tasks can run either under IRAF (via the STSDAS Fortran 77 interface) or directly from the operating system (via the SAO Host Interface)--see Figure 4. Table 1 gives a list of the names and short descriptions of the FTOOLS tasks.