My new trunk weatherstrip came in today for my 96' park Ave, and it did not come with any type of adhesive, I am not sure it requires any though, as I thought it was like the brake light seals, they had a black polyurethane like glue already inside of them.
After looking at the way my weatherstrip was installed, I am thinking maybe it was put on backwards back when I had it removed while squeezing in a custom made speaker box..

Anybody ever replaced on of these?
One side has a firm like flat area, then the other has a squishy like part to it, it seems like that should be installed facing up, but on the old it was facing down, which may have been how water was getting in past it, and ending up in my break light housing..

If anybody has any pics of a PA or similar Buick that should have a similar weatherstrip they'd be appreciated.

Also once I am sure the way it goes on, should I use some of the SikaFlex Marine Grade polyurethane sealant that I have?

Let me try to upload these two pics so maybe somebody can tell me for sure which way it goes, I am thinking the first pic, the one on the left of the flat side goes underneath the lip, so that would be on bottom, and the squishy part that seems like it would seal better goes on top, and comes in contact with the trunk lid.
It should be common sense that it is the second one that comes in contact with the trunk lid, but if that is the case it was out on wrong years ago by the custom audio guys that made my speaker box...

Watched a few videos of other types of trunk weatherstripping being installed, and I am pretty sure it has been on wrong for years, which makes sense as to why I was getting water in the trunk, and brake light housing.
So as soon as it stops raining I'll remove the new trunk seal, make sure the lip it goes on gets dried off, then I'll put a tiny bead of SikaFlex into the weatherstrip, and install it.
Then maybe my floorboards won't get wet anymore, it is possible that the water was getting in behind the break light housing, and finding a way to flow into the car.
I could be wrong though, but how awesome it would be if when I put the seal on the right way, the water stops getting in.
If it does then I can work on getting my headliner repaired, not sure I want to do that job myself, as it will be tough to get it right since I used the Dorman pins that are made to keep it from falling down more, I am guessing I'd have to fill each little hole they made before a headliner would go on totally smoothly..

I did a trunk seal replacement on older Cutlass a while back.
The new one from GM was too long and had to be cut to fit. I started at the top middle and fed around to cut perfectly.
Make sure the prep area is spotless clean, before new seal get installed.
I also used a poly sealant after install under lip to hold in place and it should add some additional water tight protection. It worked fine.
Too bad later I found out the whole wheel well was rotted out and was soaking everything, to the point I needed a bilge pump!

Squishy side to the outside (facing up) so it will interface with the surface that is being closed against it. They are installed at the factory without adhesive, but I don't see the harm is putting adhesive on the pinch weld or in the channel of the seal prior to installation.

Thanks, that totally makes sense, and to think over the years it has been on wrong, no wonder my trunk would take on water, dohhhhh!
As soon as it dries up a bit outside I am going to remove the weatherstrip, and clean the are a little better, and put a tiny bead of the marine grade SikaFlex in the channel of the seal for added protection, I am pretty sure my trunk water issue should be over after that, thanks!

They are usually cut to fit....don't cut it short ......you can force in, a slightly longer one.....the joint should be in the latch area, not the top of the trunk....I always used 3M Weatherstrip Adhesive...

Yeah this one was cut exactly to fit, and sealed where it was cut, it installed perfectly.

I got my fingers & toes crossed this time after it rains, it stays permanently dry back there!

After putting it on the right way it should, if not I'll put an extra bead of SikaFlex around the lower lip part of it, I am sure it will be good to go now though.
I am really hoping that stops the water from getting into my floorboards, I am tired of getting 1"-2" of water pooled up in the rear floorboards every time it rains!
I will be beyond overjoyed if it was as simple as correctly installing the trunk weatherstrip!