Of all the anti-theft solutions, this is assuredly the easiest to install and the most radical: you need only hook this alarm over a door handle or knob and the deed is done! Every movement of the door or handle will set off a powerful and loud alarm. You’ll be immediately aware that an intruder is attempting to break in. And surprised by the alarm, the intruder will take off as quickly! Plastic and metal. Operates with 3 AAA batteries, not supplied.