When you have 80 Bertie Bot Every Flavored Beans, go to the reading room where you buy things from Fred and George in the Griffindor House. Percy will try to stop you. if you try to go during the day, Fred and George will not be there, except on the last day of school. When you go in, you have to go to the opposite side of the table. There will be a book. Go up to it and Fred will say that it is 80 Bertie Botts. If you have enough, he will say you can go mostly anywhere in Hogwarts. This spell will only work on some doors and chests.