Bad screen grammar is as off-putting as bad spoken grammar, and the reasons for this are explained. The golden rules of crossing the line are explored, as are the different ways this tricky topic can be covered. Bad screen grammar means the editor of the finished product spends more time curing the director’s mistakes than augmenting their work—and nobody would/should choose that. The benefit of two rather than three lines of axis for two cameras covering a scene are explained and illustrated.