This is a shot up inside the RH B-Post. There is a flap along the bottom edge that is about 8 inches by 3 inches. It doesn’t do anything – I’m convinced it was there so that the B-post inner side panels could be dropped onto the inner sills and sit there during assembly. What it DOES do is trap moisture and water and is a big part of what makes the B-posts rust out so fast. It’s always in the way too, so I cut them out – on the rare instance when it still exists. It is in the bottom half of this photo.