gag station, gag

English Tech/Engineering Mechanics / Mech Engineering fin molding line

talking about the control system of this line
here are the sentences where "gag" appears

""The column headings under the gag station numbers have changed to describe what controls that gag station"

"2. Set the gag stations as required after setting the cutoff."

""Definition of the gag station reactions with the Prog. Fin On and Prog. Fin Off are possible in the Die Data & Part Option Screen."

and above all this:
""This is useful when the wiring, plumbing, or function of the ***die gag***??? is reversed from expected or desired behavior"

I seem to understand that in the field they talk about gag sequence and autogag but I cannot understand what it is, thanks!