Storm windows with no latches

First winter in an old home. In the back shed there are a dozen+ storm windows for the whole house but I cannot for the life of me figure out how they attach / stay in the windows.

Frames are wood and the storm windows are wood as well. There’s no latches, inserts, or any other protrusions/notches which might suggest a method by which they stay in place without toppling out. I figured maybe the latches were missing from age but the paint job is ~2-5 years old. Previous owners must have known something I don’t.

Do I just need to install latches on the windows or is there something I’m missing? Would like to avoid drilling holes in old frames if I’m just missing something simple.