Make sure you have some silicone handy. The seal around the sunroof panel slips on from the bottom and, for the most part, attaches snugly to the sunroof panel.

However, the action of the venting position and the movement of the sunroof can cause the seal to slide down and off the panel from time to time. The best guarantee against this is to shoot a tiny line of silicone sealant into the crack before you slide the sealup and onto the panel. This will insure it fits snugly and reinforce its hold on the panel to the point where you never need to worry about it again. The corners of the seal ring can usually be trusted to keep themselves on (tighter fit), but you might want to tag them too while your at it.

Couple other notes:

1) make sure to clean off the rim of the sunroof after you remove the old one. This will help the silicone get a good grip.

2) do it sectionally and make sure to hold the section you are fitting onto the panel firmly to allow the silicone to get a good lock between the seal and teh panel.

3) when you get the second end all teh way around to join the first you might notice a small gap between them (the seal isn't a solid loop). I don't know anyway to "stretch" the seal enough to avoid this. I usually let the seal dry in place and then go back later and fill that gap with silicon (about 3cm or so... just form teh silicon with your finger so it matches the shape of the seal).

ggood luck,
rt