Certain Teed Bryan Myrw window
A quick learner from Burke, va says:
October 7, 2016
The 3x8 by 2.5 inch window stop that prevents the bottom window from totally opening if the part is engaged.
Dave from SWISCO responded:
October 11, 2016
Thanks for posting. Sounds like you need a vent lock. I'm afraid we don't have anything in that size, unfortunately. I haven't been able to find anything that big, either. It could be that it's no longer made. Could you perhaps use something like our 26-387? See the video below for more information.