180 degree rule

The 180 degree rule is an important part of continuity and editing.
It involves an imaginary circle in which you can only film in your chosen semi-circle, two characters in the same scene should always have the same left and right relationship to each other, in order to not break the rule.
This is an example of how to accomplish the rule and how you can break it by crossing the line.



This video shows how to break and to keep to the 180 degree rule.