they are just held on by tape but there are holes and a groove in the door.
There are 'prongs' that go into the holes, but that just to keep it more or less in the right place

just a warning, lots of force needed to get them off, my old ones were deformed after pulling them off.

see my thread...
http://www.fordfiestast.co.uk/showflat.php?Cat=0&Number=308594&an=0&page=5#308594