Technical Terms for Mechanics

This has made me laugh so much, that I simply have to share it with you all. I am hoping the beloved will find this amusing in time!

On sunday we were invited to lunch and beloved decided he would drive, that was until I got in the car and heard the almighty noise; I was convinced the exhaust would fall off so we took mine instead. I said I would have a look at it, but I forgot. Today I was sent the following emails (which I commented between) :

BELOVED:
I've just checked the car. The rattling is caused by a sort of metal sheath about halfway along the length of the car and fastened to the underside above the exhaust tube - it's that which is loose and rattling about. What's that, then? Can't get under the car to have a closer look.
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I asked him how big the metal sheath was and he told me it was 18inches. I then sent a picture of an exhaust system so he could locate the parts he has and work out what the problem might be to which he said:
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BELOVED:
Mine doesn't look like that! The muffler is at the back and the resonator, perhaps, is in the middle. If it is, then the resonator sits in the rattling thing which surrounds it on the body-of-the-car side.

Well, this has been charming, but I must go : )
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I expect his descriptions make every bit of sense to a mechanic, but they tickled me pink! I shall now use 'the rattling thing' and 'metal sheath' in as many conversations as possible.