window sash part
A quick learner from centreville md says:
September 28, 2016
tab that holds window in the track and attaches to the spring
Tom from SWISCO responded:
September 29, 2016
I'm not sure what it is you're looking for, but I'd be happy to help to the best of my ability. If you can, please remove the part in question from the window and take a picture of it for us to look at.