ok so word choice on your part and my part were not exact enough I think
you asked if you had to screw into a window and ruin a window? the answer is no
2 tiny screws into the woodwork which imo are optional at least with my window type.
The screws could be replaced with a piece of wood.. or nothing.
the bracket is extremely stable and works excellent even just resting on the outside against my vinyl siding.
There is also a sliding brace that slides out in the u section to the side of the window
so the AC can go nowhere. it requires 2 screws.. to lock it into place these go into the brace and brackets on the ac
not anywhere on the window. but you could just slide them out and it locks the ac into the window.. I dont even use mine. its not going anywhere with the window closed.
and it barely fits in my window(width) so its a pain to get a screwdriver in there but doable.
edit: I added more to post
@JHZR2
If you are thinking about replacing regular window ac with these.. they are a winner. I'd buy another tomorrow full price if this one dies... that much better.