For the board : http://www.wargear.net/boards/view/Five
Thought I'll make this thread since I've been trying to make this board more popular.
You can attack Row Up from Row Down. And you can attack Col Left from Col Right.
And similarly for forting: you can fort to Row Down from Row Up. And you can fort to Col Right from Col Left.
The wrap around fort is very important and can be used to surprise your opponent. For a classic example, see this: http://www.wargear.net/games/player/597263
Also note that the wrapping around does not work between, say, Up1 and Up5.
I'll also link another game http://www.wargear.net/games/player/598273. Worth seeing while reading the comments.
For those unfamiliar with this: The button at the top right of the post (right of date) shows the turn id when the post was made. That's needed if you want to read the comments at the right time while seeing the history.
Will write more later as and when I find something important. Others can chime in till then.