The glass seal fits right into a channel on the glass,so does the body seal under the glass.
Your door to body seals are the same way. The proper way to install your new seals is to with one hand hold down on the weatherstrip and pull and push down on it with the other hand,so that your stretching and pushing it into place on the piece that you're resealing.
If your sunroof retainers are shot,we manufacture them,they're stainless steel,plus nickle dipped for added protection.
Tony