Prevent house battery drain while stored. Patented contour lock system allows switch to be used as a stand-alone unit or locked together with other switches. Control knob cant be removed while in the On or Off position, but it can be removed by switching to an anti-clockwise 45-degree position. Removable side plates on 4 sides for access of up to 1/0 cables plus a rear cover insulating the rear terminals against any short circuits. | Marinco House Battery Master Switch