dpiper said:If he comes at you with mouth open (and you have winter gloves on) ram your fist down its throat. If its got something stuck in its throat it wont be able to close its jaws (this is the only one of the above methods I havent yet proven for myself!!)
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If a dog comes at you with mouth open, with it's tongue lolling all over the place, then you're not in any danger at all. It wants to say hello and have a play.
It's the quiet fixed stare and maybe licking of the lips, tail up followed by a head on charge that you want to worry about.
Other than that, I strongly suspect that a dog can close it's jaws a lot faster than most people can push their hands forward!