How do you knock a chicken out? I would think hitting it soft enough to not fracture its skull would be hard to do. And if you hit it harder then you do fracture its skull which would defeat the painless method you are trying to achieve. Just kill the thing! There are several methods to...
http://knives.dexter1818.com/shop/sani-safe/poultry-knives/ep154hg.html
This is what I use to slice the neck and use another one just like it for processing. Hi visibility color and great grip.
Love it.