How to Install Door Sensors for a Home Security Alarm System

Select the door that will have a door sensor. Clean the interior surface of the door so it is free of any dirt or gunk. Also clean the area of the wall where you plan on attaching the main unit of the door sensor kit.

Round up a screwdriver, electric drill and a carpenter's pencil, as well as a level. You may also need a stud finder and/or drywall anchors.

Use the stud finder to locate a stud as close to the top of the door frame as possible. If you can't find a stud, you will need to use the drywall anchors to make a secure attachment to the wall.

Hold the main unit of the door sensor up to the wall. Level it, and then mark where the top of the unit is on the wall with the carpenter's pencil. Also mark the location of the unit's screw holes on the wall.

Drill pilot holes for the screws. If you are not drilling into a stud, make holes for the drywall anchors instead, then insert the anchors into the wall. Screw the unit to the wall.

Pick a location on the door and on the door jamb to install the magnetic switches. The switches have to be placed so that they will come in contact with each other when the door is closed and contact is broken when the door is opened.

Mark the location of the magnetic switches and drill pilot holes. Attach the magnetic switches. Now, set up your home security system to recognize signals from the newly installed door sensor.