Modular Terrace Kit MTK2 Red Brick Back Yard Double
This is a pair of back yards to be used with the Twin Terrace Unit. They're double ended, so you can rotate them through 180 degrees to bring greater variety, and since it's designed to 'slide inside' the back of the terrace, it also allows for a flexibility of yard size.
The dividing wall is included, but the outside boundary walls come as a separate unit to allow for yet more variation (MTK2 RB1 GW). The 'exploded version' to the right of the screenshot should make positioning and construction clear.