Hi. I'm opening up what was previously a doorway in what I think is a stud partition wall. I've taken off the plasterboard and there is what I can only describe as a piece of wood stuck in the middle.. I assume in the hope that it will support the plasterboard, attached to the sole plate with some kind of plastic thing and a couple of screws.. I've taken this off.. But there are also two small pieces, in each upper corner running diagonally from the studs on either side up to the piece that runs across the top of the doorway.. I'm not sure whether I should remove these or not.. is it safe? Any help or advice greatly appreciated.