The continuity approach to editing which dictates that the camera should stay on one side of the action to ensure consistent spatial relations between objects to the right and left of the frame. The 180-degree line is also called axis of action.

for example filming a conversation requires that the placement of the camera should not present the two speakers in such a way that they both look to be talking towards screen left (or both talking towards screen right) when they should be seen talking in opposite directions.