1969 Dart 2 door rear side window glass install

Glass was pulled long ago, I screwed the bolts in when I pulled the glass. The bolt has a big washer and there was also a round plastic piece on the bolt, is there supposed to be 2 round plastic pieces one on each side of the glass? Or if just one plastic piece, does the plastic piece go on the other side from where the bolt & washer go thru the window?

Thanks!