Door Alarm Wedge will scare off intruders and sound an alarm. Simply place the alarm behind any door. If an intruder attempts to open the door the wedge-shaped design will prevent it from 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 that is not included.