When an XSPEC build is intended for many users across a system, it is also possible for the installer (or whoever has write access to the distribution and installation areas) to globally customize XSPEC. This is done through the file global_customize.tcl, located in the Xspec/src/scripts directory. (This was done in the xspec.tcl file prior to v12.2.1) Any of the customizations mentioned above for the individual's own xspec.rc file can also be placed in the global_customize.tcl file. After making the additions, run ``hmake install'' out of the Xspec/src/scripts directory in order to copy the modified global_customize.tcl file to the installation area. This additional code will be executed for all users upon startup, BEFORE any of their own customizations in their xspec.rc files.