mine was between the master and proportioning valve on the front brake line.
I would pump up the brakes set the line lock and mash the loud pedal. never had an issue. I did it this way because the cars "was" going to be a manual trans. this left me free to operate the clutch.
I have also seen them installed on the line to the rear brakes after the prop valve to stop the rear brakes from working.
which is better ? dunno ?
I do like the idea of it in the rear line so you can modulate the front brakes for John Force style burnouts. but I don't know how well it works.
