Ninth-City Car Auto Vihicle Side Post Battery Master Disconnect Cut Off Switch Isolator Easy to Install:1.Disconnect ground (-) cable from battery and attach it to mounting flange side of the threaded hole on the switch. 2.Using the supplied bolt,attach switch to (-) battery post.The mounting flange on the thru-hole must contact the battery post. 3.Turn black knob fully clockwise to connect battery power.To disconnect power,turn knob 1/4 turn counter clockwise.Knob can be removed for anti-theft.