3 For added security and drain prevention, I am installing a master shut-off switch in the trunk. If I was keeping to the NHRA rules, the switch would need to be accessible from outside the car in the event of a problem and it would also need to interrupt the alternator wire as well. Again, since I am just doing this job to clean up previous work, I will not be worrying about those parameters. I disassembled the switch and used the faceplate as a drilling guide. After drilling the large hole with a hole saw and the small one with a regular drill bit, I put the switch in and moved on to getting the battery in place.