How does shield bash work

[Riva]

I have the shield that grants bash but there doesn't seem to be a choice to use the ability. Is this broken or is it some sort of passive effect?

[Enexemander]

It turns the shield into an offhand weapon. If you check your inventory screen, you'll see that with the shield equipped you'll have 2 numbers under accuracy.

[dukefx]

And before you come asking: "does two weapon style work with it?" the answer is no.