Alarm Security Bar sounds when door knob is touched! Get extra peace of mind against intruders while at home or traveling. Heavy gauge steel bar adjusts to secure any door and emits a powerful siren or barking dog sound to scare off strangers whenever doorknob is disturbed. Rugged yoke fits under knob and sturdy gripper base anchors unit against floor. Use on any door; extends from 29" to 43". Uses one 9V battery (not incl.).