She invented a simple device - a small metal disc with a precisely measured hole in its centre placed in the fuel line.

When he tries to remove his tool, however, the metal disc sticks to the tweezers.

This flat, light and smooth metal disc comes with a variety of loops, so you can wear it on your wrist, around a belt or on a piece of clothing.

This was a small metal disc with a hole in the middle, fitted into the engine's carburettor.

The inner rotating metal disc typically had a number of studs on its outer edge.