SECRET BOOKCASE DOOR hack. Jen always wanted a secret room (who doesn’t?) She turned that fantasy into reality with two BILLY bookcases. And it’s easier than it looks. Head to ikeahackers.net for the full instructions. #ikeabillyhack #ikeabilly #ikeabillybookcase #secretroom #murphydoor #diy #ikeahack #ikeahackers #hiddendoor