A quick learner says:
August 24, 2014
This is the tab on the top right and left side of the window that opens and allows the window to be pulled inward. The part number is 8615X7
Paul from SWISCO responded:
August 26, 2014
Thank you for posting. This part is known as a tilt latch. Your part looks a lot like our 26-317. Check it out and see if you agree.