Sometimes you just forget to close the garage door. But if "sometimes" is closer to "usually" for you, you may run the risk of having your garage emptied out by opportunistic passers-by, and you will certainly pay more to heat your house. Chamberlain"s Clicker Garage Door Monitor helps you minimize the likelihood that you"ll leave the biggest door in your house open. The device mounts easily without tools to your garage door via a Velcro strip; if your door is open, the sensor sends a signal to the monitor, causing a red light to flash. The monitor may be plugged in anywhere in your house where you"re likely to notice the flashing light. Depending on your garage-door habits, this device could help prevent theft and lower your heating bills. Includes lithium battery.--Josh DettweilerWhat"s in the Box Sensor, receiver, AC adapter, double-sided Velcro fastening strip, lithium battery