Shared Yard - Turn into split yard

[Charlie Tillett]

Hello, I am a first time homebuyer looking to house hack. I found a duplex with a shared backyard and a deck directly in the middle of the yard with both backdoors exiting onto the deck.

I have a dog, and would like to keep him out of my neighbors yard. How could I turn this shared deck and split it into two separate yards? 

[Jonathan Styer]

I would just build at "wall" down the middle of the deck in line the the fence, should be pretty easy.