We have an old winter garden with a thick glass roof.
In the summer it gets intolerably hot and blindingly bright in there, so we don't really use it much.
We didn't have it in our budget to get custom-made sun curtains and it required construction that would have damaged the old wall of our house.
So, all in all, not a good solution.
That's how the idea of using magnets came about.
We attached a large white sheet to the inside of the roof with 45 large Q-19-13-06-N
Thanks to the metal cross beams this was a walk in the park, although the sheet weighs about 10 kg!