back when i was serving my time, i was in a rover dealership()
anyhow, had a car back for strange knocking noise intermitantly,
we had it in several times and couldn't find it anywhere,
after months we finaly found the problem,
there was a marble inside the sill, must have been left in when the shell was
being manufactured, some bored factory worker having a laugh,
took us months of searching, couldn't find a thing,
think its funny as fook now but i remember not being amused at the time