The film dot is a raised area in one corner of the film. It is used to determine right from left on the processed film. When taking the radiograph, the dot is placed toward the occlusal (biting) surface and toward the tube head.

Dot location on cassette

Raised dot on unprocessed film

Film cassette with circled film dot toward occlusal surface of incisors

Film dot circled on cassette positioned toward right maxillary premolars

Film correctly positioned to expose left maxillary premolars.