The initial idioms of the letter B

be cast in cement	be cast in concrete
be cast in the same mould	fall between two stools
be caught in a time warp	be caught napping
be caught off (one's) guard	be caught on the hop
be caught short	be caught with (one's) pants down
be caught with pants down	be center stage
be centre stage	be chafing at the bit
be champing at the bit	be chasing tail
be chief cook and bottle washer	be child's play
be chilled to the bone	be chilled to the marrow
be chomping at the bit	be cleaned out
crystal clear, be	be climbing the walls
be close to home	be close to the bone
be close to the mark	be clued in
be cocksure of (oneself)	be coining it