A home owner from Tampa,Fl says:
September 5, 2016
I'm not sure what this part is called but I know it prevents the windows from rocking left and right when opening and closing.
Paul from SWISCO responded:
September 8, 2016
Thanks for contacting us. I think you may need a face guide. It's hard to tell what yours is while it's still installed, but take a look at our 67-014 and let me know how well they match up.