A detailed investigation of theatre frame has seldom been undertaken, and far less have non-Western theatres been taken into account for the definition of a universal frame theory. This essay attempts to adjust frame conception and analysis to the needs of the performance system, with particular stress on the semiotic function of the frame, and considering the outcome of different disciplines such as art criticism and linguistics. Through a review of the opinions of Goffman, Simmel, Ortega, Kernodle and Schechner, it explores the idea of frame as a passageway into the art work (therefore into the performance) and focuses on the definition of frame as threshold, lintel, and bridge. This allows to define a possible set of time and space delimiters, inscribing the performance itself within a frame. Examples are taken from theatre practice all over the world.