Our tester pen is materials , practical and Self-check before use , please hold the pen tip with hand and for touch the tail with the other hand.When the light is on , it means the tester pen is normal and has sufficient power hand touches the bottom of pen , and the tip of pen touches the wire The breakpoint is where the light goes out.Easy to hot wires This is a flexible tool that provides a unique ability to check holiday lights and power to they are capable of being lit and used As long as it is close to the insulation of the wire , the for shell of the electrical appliance , , When the light is on , it means that the line is live, Manufacturer: Watreketal