Okay, say if you are sword fighting, press b. That way you can block, you can hold it, but if it was successful, it allows you to block for 5 sendonds ( not like 1 2 3 4 5) (more like 1 1thousand 2 2thousand)
Oh btw, so you can't keep blocking over and over so it's almost EXREMELY hard to kill, it doesnt't always work, sometimes when you block you still get hit.