This week we started the sugyos of Hatmana. We learned the Halachos of not being able to do Hatmana (completely insulating food) even with something that doesn’t add heat, however if it is done before Shabbos it is Muttar. There are certain instances where the the Rama allows for Hatmana and one of those cases is if it is only partially covered, in that case the Rama holds its not Hatmana. However the question arises when a part of the top of the pot is exposed, what is the amount of exposure for it to be permissible. The Poskim say that as long as there is enough opening on top for a significant amount of heat to get out then its mutar.