It is a seperate mesh using texture/black32.blp and the unshaded flag.
If you use milkshape (Which is unlikely if you're aiming for Reforged.):
To make them fit squares I just fit them perfectly in the default milkshape grid, and the scale them by 3.2 on each axis.
Generally, my walls is 3 by 1 in size (3 grid tiles tall, 1 grid tile wide.). If you want to make them fit together.
Feel free to pm me if you have other questions. More walls = more better
A lovely model for terraining, but there are some small issues that might make use of it a bit less hassle.
The number extends of the model do not match the number of geosets. That might be fixed with recalculating the extends or fixing them by hand.
Please fix this if you are able to.