The 180-degree rule is a filmmaking guideline that establishes an imaginary line, or axis, between characters or objects in a scene. By keeping the camera on one side of this axis for every shot, the spatial relationship between the characters or objects remains consistent, with one always being framed to the right of the other. Crossing this axis line with the camera is called "jumping the line" and should generally be avoided.

1. 180 degree rule
In film making, the 180-degree rule is a basic
guideline regarding the on-screen spatial
relationship between a character and another
character or object within a scene. An
imaginary line called the axis connects the
characters and by keeping the camera on one
side of this axis for every shot in the scene, the
first character will always be frame right of the
second character, who is then always frame left
of the first. If the camera passes over the axis,
it is called jumping the line or crossing the line.