Demagnetisers work by disorienting the small pockets of magnetism present in all materials. These pockets are referred to as "domains;" and in magnetised materials, each domain is lined up so that they all point in the same direction. Normally demagnetised materials can accumulate magnetisation over time by being near a magnetic field. Screwdrivers are prime examples of devices that should be run through a demagnetiser, as they can cause unwanted parts in a toolbox to stick to them if they become magnetised.
Connect the alligator clips to the ends of the coil.
Connect the other ends of the alligator clips to the battery terminals. Give yourself enough wire to be able to move it 3 or 4 feet. Attach the negative wire to the bottom of the coil and the positive wire to the top of the coil.
Move the coil along the device to be demagnetised in all directions. Run the face of the coil lengthwise along it, move the coil closer and farther away and twist the object around if possible.
Test the demagnetiser by running it over a magnetised screwdriver and putting a screw within a centimetre of the screwdriver. If the screw moves toward the screwdriver, then repeat the process.
Disconnect the alligator clips from the battery when you have finished demagnetising. Do not use the demagnetiser near credit cards or computers. This can accidentally erase card data or destroy computer components.