Possible Clues:

• One of the things actors have to go through secretly in role reversal at The Gate?
• Hinged floor opening
• Gin before opening may let down an actor
• Secret exit, maybe
• A gin before opening may let an actor down
• Cause of an unexpected fall
• Hinged flap in floor
• Magician's secret, perhaps
• *Secret stage exit
• The cross bit will open up