There is also a shieldbash in dev1257, former 1257 aD mod.
Make it as it is there. When you block and press left mouse button, there is a chance that your char hits with his shield. When you works people stumble or fall to the ground.
In 1257ad it works like that, but it doesn't always work. Sometimes nothing happens. And it is a risk for shielders, because the moment they bash, they are open and can be shot......experienced that alot of times, although it's singleplayer^^
I shieldbashed someone to the ground and got shot meanwhile