[MF_U] Allows you to put items in equivalent rooms, meaning you can put an item in two (or more) variants of the same room and have the item removed from all of them at once.

e.g. In the vanilla game, if you skip Bob you are not able to collect him later due to the two room variants used (Sector 3 room 0x06 and Sector 3 room 0x18) one of which contains no Bob. By using this patch and and adding a missile tank to room 0x18 Bob can be collected later.