Electricity: Your home is filled with many electricity paths that spider web through the walls of your home and they all lead to the electric panel box. Many issues start at the outside of your home, the drip loop coming into your home, it should be a large downward loop so that any water that runs down the line will drop off before entering the conduit leading to the inside panel box (water and electricity do not mix well). Throughout the current paths there may be breaks in them to add service devices such as lights or electrical outlets, these must be contained in fixture boxes that are called gang boxes, it allows space for the wires and the component to fit and not interfere with any insulation, dust or wood components causing a fire.