The Mapping constraint lets you map one Parent/Child relation to another Parent/Child relation.
The Mapping constraint requires the following objects:
Child object of the Parent/Child relation that inherits translation and rotation from the source Parent/Child relation.
Parent object of the Parent/Child relation that inherits translation and rotation from the source Parent/Child relation.
Child object of the Parent/Child relation that sends translation and rotation information to the constrained Parent/Child relation.
Parent object of the Parent/Child relation that sends translation and rotation information to the constrained Parent/Child relation.