Since the Common Room has been locked (the Great Lockout of '78) and all students forced out, the Gryffindors have had to make other arrangements for sleeping, eating, studying, dining, etc. Conveniently, the long dining tables of the Great Hall have also disappeared, perhaps under the same strange circumstances that led to the lockout....

As it is, the entirety of Gryffindor House will be sleeping in thick, warm, purple bags with silver stars embroidered on them, right in the spot where their fancy table used to be. The bags are a Hogwarts' specialty, used only in certain circumstances, and although they are no match for a real mattress, they'll have to do for now.