Cautious Shield Gives a 6+ armour save that can be combined with other armour as normal. The bearer can force one model in base contact to lose 1 Attack (he can choose which Attack in the case of opponents with different Attacks, such as cavalry models)...
In addition, the model can decide not in attack at all, but to wield the shield with two hands and concentrate on defence. If he decides to do this, the chosen enemy will lost 2 Attacks. The player must declare which way the shield will be used at the beginning of each Close Combat phase. before any side striker blows.