We all looked at each other, and the mechanic asked, "What is a seven-hundred-ten?"
She replied, "You know, the little piece in the middle of the engine. I lost it and need a new one. It had always been there."
The mechanic gave the woman a piece of paper and a pen and asked her to draw what the piece looked like. She drew a circle and in the middle of it wrote 710.
He then took her over to another car which had the bonnet up and asked, "Is there a 710 on this car?"
She pointed and said, "Of course, it's right there."
Spoiler: