Roof Trim Help

hi guys, has anyone had a problem with the black rubber trim that runs the length of the car roof (outside not inside)? mine has come loose near the windscreen,iv lifted up as much as i dare to see what holds it on. it looks like a plastic clip of sum sort. I tried clipping it back in but it wont catch. any ideas ? is there a nack to it? or where wid i get a new one and how do you fit them?



thanks in advance