Other sheep

Jesus is speaking in Jerusalem, to Jewish listeners. Yet he says he also has sheep from outside this fold. Most interpreters think of people from other nations. Notice the two words. A fold is an enclosure. A flock is a group that follows one shepherd. The King James has fold twice; the Greek doesn't.

So Jesus doesn't promise one big enclosure that everyone has to get into. He promises one shepherd, who knows sheep from all kinds of folds. It isn't the wall that makes them one flock, but the shepherd. That means the flock includes sheep you would not have chosen.