The BAMA Rule, otherwise known as the "Buccal Object Rule". It's something you learn in radiology. There is only one school that calls this method of determining the location of objects on and X-Ray the BAMA rule, of course it's the University of Alabama School of Dentistry. It's much easier to remember if you think BAMA (Buccal Always Moves Away).
If you have an object on a radiograph that you really can't tell whether it is in front of or behind another object (buccal or lingual), you can take another x-ray from a different position to determine if the object moves in relation to surrounding objects. If you move the beam at an angle comming more from the right and the object seems to move away to the left, then the object in question is to the buccal. Buccal Always Moves Away (BAMA).
Here is a link to an article that explains in more detail: BAMA Rule