Bang/knock your/their heads together - Idioms by The Free Dictionary
bang/knock your/their heads together
knock (people's) heads together
To scold two or more people harshly. If you two do something this stupid again, I'm going to knock your heads together!
bang/knock your/their ˈheads together (informal) force people to stop arguing and behave in a sensible way: I’d like to bang those stupid politicians’ heads together.