In alt.home.repair, on Wed, 30 Dec 2020 15:07:41 -0500, Clare Snyder
wrote:

On Wed, 30 Dec 2020 08:34:45 -0800, Bob F wrote:

On 12/30/2020 7:13 AM, FromTheRafters wrote:
Rem Ram submitted this idea :
I’m getting a draft through these holes in my window frame. Do these
holes have a purpose? Can I cover them to stop draft?
https://www.homeownershub.com/img/12p9

Just a wild guess, but it might be an access hole for attaching whatever
acts like a counterweight these days. If so, it should have had a cover
for it.

My guess from the pic is that the latch at the top edge of the lower
window pushes a plunger into the hole to securely hold the window open
only that much, so burglars can't push it higher. But I have little
experience with modern windows. There would have been a plastic cap in
the hole originally with a depression for the plunger.

No plunger - that latch is for the "tilt" feature.

It could be for both. The handle on the slide is in the middle. All
the way away from the frame to tilt the window in, and all the way to
the frame to go into that hole.


And it really does look like the upper inner pane is missing.