Simply put this alarm behind any door. If an intruder tries to open the door, the wedge-shaped design not only stops it from opening but it also activates the built-in alarm. The alarm will scare off the intruder and alert you to the attempted entry. An adjustable sensitivity switch prevents tampering.
For travel, just toss this lightweight unit in your suitcase. The on/off switch will prevent the unit from accidentally sounding.