Crop Marks is part of 'XPress Scripts 1.0' a package of twelve AppleScripts for use with QuarkXPress 3.3.
Crop Marks sets crop marks around selected text boxes or picture boxes. You can configure crop mark length and offset distance in points via two dialog boxes. The default crop marks are 0.25 pt wide and its colors are in registration.
Quark Xtensions generally (always?) work faster than scripts and this is no exception, particularly with multiple box operations. However there can’t be many Xtensions that give you the option of crop mark length and offsets.