Quiz - Guess the mysterious knock

[broady69]

I have an annoying knock coming from the car and for the life of me I cannot find find it. any guesses.

Location: Middle to Rear of car and low down....could be underneath back seats.

Sound: Sounds like an empty plastic coke bottle being knocked against the body.

When: Seems to be related to up and down motion but even the smallest but sharp motions.

Any takers?

[Wolfgang]

My guess is the rubber things that hold up the parcel shelf when the hatch is open hitting the trim in the boot.

What's the prize for the correct answer?

[broady69]

Beers OK for a prize?

[Wolfgang]

Beer surely is OK for a prize.

[jettapilot]

This sounds very familiar. I'm sure a forumm search will find the winning answer.