DIY House Alarm for Intruders

Clip the insulation off of two pieces of insulated wire, exposing the metal. Wrap the exposed portion of each wire around one jaw of an alligator clip or spring-loaded wooden clothes line. The wires should come into contact when the clip's jaws close and be separated when the jaw's clips open.

Connect the free end of one wire to the positive terminal of a 1.5 volt buzzer alarm. Connect the free end of the other wire to the negative terminal of a 1.5 volt battery case. (Don't put the battery in the case just yet .) You can purchase both items at a local Radio Shack or similar store for a few dollars.

Connect the negative terminal of the buzzer to the positive terminal of the battery with a third piece of insulated wire.

Glue the battery case, the buzzer and the alligator clip to a piece of wood, making sure that the clip can still open and close. This combines them into a single unit, which makes them easier to move.

Punch a hole in a sturdy piece of cardboard and run a length of string through it. Connect the free end of the string to the corner of the door, window, or entryway you wish to secure. It should be attached to the side farthest away from the hinges, or the side closest to the jam: the first part of the door or window to move away from the frame when someone opens it. Use a tack or thin nail and make sure the string is tied to it firmly; you don't want the string to become disconnected from the door.

Place the cardboard between the jaws of the alligator clips so that the two wires don't touch. It will act as the circuit breaker, keeping power from reaching the buzzer until someone trips the alarm.

Drill several small holes in the piece of wood -- somewhere towards the center of the wood, away from the alarm components -- and screw it into the wall near the door or window with drywall screws. You can also nail it to the wall with a hammer and nails, though that won't be as secure as drywall screws.

Place a 1.5 volt battery in the battery case. The alarm is now armed. When someone opens the door or window, he will pull the cardboard free of the alligator clip, completing the circuit and causing the buzzer to go off.