We don't have these so I don't know what I'm doing. As it says in the title, it seems to open just a crack and is letting in a draught. I've slammed it shut but it's not properly. Do I force up the plastic bit at the top? I've sort of tried but would have to really force it and I obviously don't want to break it but I can't see any other type of fixture so it seems like that or nothing. Have messaged the owner but no reply so far and it's really cold!