Adding Inline Switch to String Lights

I started doing this with making bottle lamps and now I am adding switches to my incandescent Christmas lights.

#1. With the string lights plugged into power, use the no contact volt detector to determine which is the hot wire.

#2. Mark the hot wire with a sharpie or tape.

#3. Unplug the string lights from power source and use wire cutters to cut the hot wire.

#4. Follow the instructions for the installation of the inline switch.

#5. Plug the string lights back into power and turn on.