Abstract: A burglar alarm is disclosed which detects the unauthorized opening of a door or window. The device has a longitudinally adjustable rod which extends between the burglar alarm and the moveable portion of a closed door or window. An attempt to open the door or window activates the burglar alarm causing the alarm to sound. A built in detent within the burglar alarm holds the alarm in the "on" position until manually released. A releasable locking fabric mounts the alarm to an adjacent stationary door or window frame. The alarm is readily separated by hand from the releasing locking fabric for easy opening of the door or window in the event of an emergency requiring a rapid exit.