The Crossing curtain is mainly used to make actors appear or disappear.
You can give the surprising impression of having crossed a wall or, when the curtain is used as a projection surface (for example with the realization with white LBE - Perolastic) of having crossed a screen, physically leaving a filmed scene, or entering it.
Or instead you can give the impression of having materialized from the darkness (for example with the realization with black LBE - Perolastic) or of disappearing suddenly into it.
It is possible to play with the transparency and reflection to the light of the materials, while making the actors pass from one side of their surface to the other, for example with the Tripolina string curtains.
Or the silhouettes of the actors can be rear-projected onto the surface of the backdrop (white LBE - Perolastic) until the actors cross it and continue the action in front of the backdrop itself, frontally illuminated, the possibilities are many.