STEERING WHEEL BAR LOCKS - The most popular is The Club, a steel bar that clamps on the steering wheel and makes the vehicle impossible to steer. They are an effective deterrent because of their imposing presence on the steering wheel.
 

HOOD RESTRAINT - A device that prevents full access to the under the hood components. These can include a chain which allows a hood opening of approximately four inches, a mechanical or electrical device that physically locks the hood down, or a mechanical or electrical device that prevents the factory-supplied hood mechanism from operating.