e.g.
_____
_O.P_
_O.P_
_____
In this case, assuming all strengths are equal, Players (P) will only be able to make one-die blocks against opponents (O).
_____
_O.P_
_O.P_
__.P_
Here, the player in the middle may make a two die block against the lower opponent, as he has a team mate who is outside the tackle zone of the second opponent assisting the block.
_____
_O.G_
_O.P_
_____
If we give the upper player the guard skill, he can now assist on blocks against either of the opponents allowing Player P to make a two-die block against either opponent.