Simply place the door stop alarm behind any door. If an intruder attempts to open the door, the wedge-shaped design will prevent it form opening and activate a 120 db alarm. The alarm will scare off the would be intruder and alert you to the attempted entry. An adjustable sensitivity switch prevents tampering. When traveling, just toss this lightweight unit in your luggage. The on/off switch will prevent the unit from accidentally sounding. Requires one 9 volt battery.