The initial idioms of the letter B

be on top of the world	be on uppers
be one card cards short of a full deck	be one up on
own person, be one's	be onto
be open to [abuse etc.]	be open to (something)
be out	be out for scalp
be out of brain	be out of depth
be out of element	be out of hands
be out of head	be out of (one's) depth
be out of here	be out of league
be out of mind	be out of mind with [boredom etc.]
be out of (one's) hands	be out of square
be out of the wood	be out of touch with
be out of tree	be out of way
be out of (one's) league	be out on ear
be out on the tiles	be out there