It's foam maybe 1/32" thick with either one or both sides adhesive. Comes in either small pads or a despenser like "Scotch" tape.

 

Ok where it is.....unlatch the top. The part that is still on the top its self is surrounded by a piece of plastic.(THAT IS WHATS #%(#*# RATTLING!) Place the tape inbetween the plastic and the metal.

The plastic slightly wraps around the top of the metal. I have no camera so I can only describe.

Only problem I found was once that rattle disapeared I heard other noises(not rattles but noises) Do this with caution. Though that rattle was driving me up the wall!

 

I had the same problem and noticed that there is signficant wear on the strikers attached to the windshield frame.
I have them replaced and the rattle is gone.