Grid Overlay for Maps?

[Bolo]

Hello Blitz,

Can someone tell me how to create the grid overlay that people use when creating a new scenario map? I think there used to be a "how to create a map" guide somewhere on here (not Huib's although that one is great and I am using it too) but I can't seem to find it.

After I get my map done, so in about 17 months, I'll probably be back asking OOB questions!

Thanks,

Dan