Hello again!

I am back with another question. How do you dismantle the roof gutter covers? I mean the black 2cm wide / 2m long covers that host the small covers for the roof rack mounts.
One of the 4 small covers does not stay in place as the piece inside the gutter has slided and I want to repair this.

Thank you in advance. I don't know exactly the name of that part in english and I was not able to find at least one picture of it

R.