Place a ladder against the wall.
Mount a motion sensor at the top of the wall in a corner just below the ceiling, using wood screws and a Phillips screwdriver.
Angle the lens in front of the motion sensor toward the center of the room or area at a 45-degree angle, so that it can detect motion throughout the length of the area.
Hold the motion sensor upside down
Mount the motion sensor to the wall, using wood screws and a Phillips screwdriver, about 4 feet up from the bottom of the wall.
Adjust the lens in front of the motion sensor so that it is parallel with the floor.
Angle the sensor lens slightly up so that pets and small children are beneath the lens's field of vision.
Have a small child or pet walk beneath the motion sensor with the security system turned on to verify that they won't activate the sensor.
Open the control panel lid on the side or bottom of each motion sensor; if a screw is used to hold the lid in place, loosen the screw first with a Phillips screwdriver.
Set the "Day/Dusk" dial inside the compartment to "Day" if the motion sensor is used indoors, and "Dusk" if the motion sensor is used outdoors.
Adjust the motion sensor's activation speed ("Sensitivity" dial) fully halfway on sensors used indoors to avoid a false alarm and fully counterclockwise on sensors used outdoors to instantly activate any light attached to them.
Adjust the length of time the light sensor stays illuminated. For an outdoor motion sensor, adjust the "Time" dial to 15 seconds of illumination.
Close the lid and, if applicable, tighten the screw with a Phillips screwdriver.