Wiring a single light switch is the simplest of all light switch configurations to wire. Two-wire Romex is run into the light switch box where the black wires are run through the switch to close or open the electrical circuit to the light bulb. The white or "neutral" lines are tied together with a wing nut as shown in the diagram. That's it. Wiring a light switch is one of the most common wiring jobs for any home, basement, or garage.