It's funny, I just hunt wood ducks. The best call I've ever had was one my dad made out of a 20 gauge shotgun shell. He shaved down one side of it where it made a 45 degree upward angle from the brass fitting to the top of the unshaved side. You just place your thumb over the hole, leaving just a little bit of a gap between my thumb and the unshaved 'wall' and blow.