Install the AAA battery use, place it under the door, and the door stopper alarm in "on" status, when door pressure is applied, the door alarm will be triggered while making an extremely loud 95db alarm; the door stopper alarm in "off" status, it can be used as common damping rubber base door wedge, hold door in the open position, no any loud alarm sound. The Door Stop Alarm offers a practical, inexpensive means to help protect yourself and safeguard your belongings. The Dorm Stop Alarm is battery-operated with a built-in siren. It is portable and doesn’t require any wiring or complicated installation making it ideal for bedrooms, apartments, and dorms as well as for hotel rooms when traveling. Pressure from an inward opening door sets off a 95 dB alarm that is likely to startle and scare off an intruder and wake you. Also, the anti-skid pad helps prevent the door from opening.