What does a cage look like?

[Ancalagon]

On my dwarf team I prefer open cage. I mean, I usually have some empty squares between ball carrier and rest of cage. Although is true a Wardanger could get into, he should blitz using 1 dice and after that, get the ball and take it from the cage without jumping (or send another player into the cage). I think this won't be an easy maneuver for the other player, and helps you to move the cage much more easily

[Grumbledook]

Traditionally its a confined space with metal bars.

[Bob-the-Fish]

I generally play the 4 post cage when I use one.
X_X
_O_
X_X
Of course there's always ways to break them (if there wasn't the game would suck ). Using players with gaurd can always help stop the leaping blitz and of course keeping another spread out line of players to keep other players away. Also, make sure there is never an opposing player touching one of the corners after the end of your turn. If there is, a simple block will break your cage open and expose your ball carrier. And always try to keep the rest of your team spread out. If they get lumped together, it gets difficult to move down fieldand you opponent can just move slowly backward and surround you leaving you with no options.
I also use a sideline version sometimes like so:
X_X
_O____
SIDELINE

The same rules apply but it frees up 2 more players, but a leaping blita can put you out of bounds so watch out.