Cat-flap

Harry Ufford opened his front door, and his animals, from the yard, came bursting through the cat-flap in the back door and rushed on him.

1985, Derek Albert Pearsall, The Canterbury Tales (in his introduction to Chaucer's Miller's Tale), Routledge (UK), →ISBN, p. 182, We could find our way blindfold about old John's house, with its cat-flap in Nicholas's bedroom-door.

While she's distracted, Batman and Robin make heroic, synchronised leaps off the fridge onto the lino and crash hell for leather, one after the other, through the cat-flap. The cat-flap's plastic frame collapses in pieces on the floor behind them.