This is not a "SWITCH" and does not disconnect at the turn of the knob lie the "green type" does. You will have to turn the knob all the way off and separate the terminal to disconnect the battery. It is easier than removing the whole terminal from the battery, but not as easy as just turning a few turns on the knob.
They are too easy to break, I had broken two already, but I saved the parts to make a new one. I suggest to buy 2 or 3 at the first time you do.