Wiring the Shop
The wiring in my old gear shop was a fickle monster. It worked well, but so many employees had laid new wires for stereos, cash registers, and alarm systems during their short tenure that no one knew which wires ran juice to each place. Thankfully the shop owner had a surefire system to figure things out. When we needed to change the wiring to block off a part of the building we were going to rent to a mosque, we would simply cut wires and then tested things to find out what wouldn't work. Losing the stereo really sucked, but it wasn't as bad as the alarm system we had to listen to until the company could be contacted to remotely shut it off.