I'm sure that you are referring to that door sill plate , the black plastic
strip. I have discussed this online and IP with many ppl about this
"annoyance" design. This is a design flaw that can eventually cause the door
sill underneath to rust if water accumulates, which it will on an S series
every time you wash it or it rains. I frequently noticed this on customer's
S cars.

That strip is attached by 5 or so brass push clips that press into thin
slots on the body to attach it. The water has nowhere to go and is held
under this plate and will eventually cause rust. On my SC2, I had to gently
pull this strip up every time I washed the car or it rained heavy, dry it
and replace it. That's one of my pet peeves with the S series.

AFAIK, there is no drainage there on any S series, only the metal clips and
holes. You can do either one or the other, replace the strips with brand new
ones and they will seat better. OR - seal the plates on, making sure that
all the edges are sealed. I was considering 2 sided tape as this is less
intrusive and more sure than glue. You will have to use a tape the width of
the plate to properly seal the plate and prevent water from getting
underneath. And the tape will be removable, glue is permanent. Replacing the
strips is the most costly but will greatly reduce the water retainage, yet
you will still have to dry that area every time it gets wet or it wil
continus to rust.

BTW - there is a chemical called I think - Great Stuff rust converter
liquid. It will convert rust to black primer and kill any rust that htis
problem has caused and help aid in preventing future rust. Careful, it is an
acid, keep it away from plastic and good paint.

Best of luck though.