Works when opening or closing the door 1 - Put the device on the door from the inside 2 - Put the small magnet on the edge of the door 3 - Put the arrow on the magnet facing the red arrow on the device 4 - Keep a distance of about 1.5 mm between the magnet and the device 5 - After testing the device, remove the sticker from the outside and then stick the device 6 - For more stability, use a screw and fix it from the battery compartment One piece left