Year: 1983
Description of problem (please be as in depth as possible):
Probably a stupid question

i recently bought this to secure my carpet down, whilst allowing it to be removed:
http://www.minispare...=...7527&title=
Ive uploaded a picture of the 3 parts that i presume are used in each clipping point.
I can see how they go together, but which part do i stick to the carpet, and which to the chassis. ???

and is the black part necessary (i cant see what it does, the silver parts clip together fine without it)?
Thanks.