I have a two part question about terrain construction:

1. I want to give my terrain a vertical thickness. i.e. I want there to be a "box" underneath the terrain. Do I need to make it a solid and use the solid tools? How do I make it a solid?

2. How can I divide a large area of terrain into separate pieces so that I can work on them individually and then later piece them all back together to make one larger terrain model made up of multiple components?

Thanks for the help!

sb