Joining Terrain Mesh
Start by creating Two 320 x 136 Terrain Mesh
Put them next to each other
Make your hills

Select both Terrains
Press "V" Pink and green sqaures should appear round your Terrain Mesh

Hold Down Control and Click On Two Sqaures (Two Sqaures have to be next to each other)

Press Ctrl + K
It Should Of Moved The Two Pieces Of Terrain Together

Do The Same with the Rest

Youve Done It

Spliting Terrain Mesh
Create A Terrain Mesh ( 512 X 512 ) Grid ( 9 X 9 )

Put a 128 x 128 Caulk Square in the middle

Select the Terrain
Now Press "V" Pink and green sqaures will apear around your Terrain

Now hold down shift and click on the Pink and green line next to the Box

Press Shift + Ctrl + X
It should of cut the patch

Do that all around the Box
Then Select The Caulk Box and Delete It
Delete the grass right in the center (Underneath where the box was)

Delete it
You should be left with this :

You've Done It
