What is a 710 knob? (3)

A few days ago I was having some work done at my local garage. A blonde came in and asked for a seven-hundred-ten knob. We all looked at each other and another customer asked, 'What is a seven-hundred-ten knob?' She replied, 'You know, the little piece in the middle of the engine, I have lost it and need a new one' She replied that she did not know exactly what it was, but this piece had always been there. The mechanic gave her 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 its hood up and asked 'is there a 710 on this car?' She pointed and said, 'Of course, its right there' pointing to the upside down oil cap
She then went home, dyed her hair brown and changed her name to Kim

Not going to go near this one.

geo