What button do I use to dig in Black Ops?

I'm not sure if this is the right forum or not for this question. I am playing Black Ops on the PC and I'm in the tunnel where I have to dig out. It says to use unbound for dig. Now I undertsand that unbound means there is no key set for this move, so I need to go into settings and set a key for it. No problem. The problem is that there is nowhere in settings where I can designate a key for dig. So everytime I try to get out of the tunnel, I die. Either I'm just not seeing the dig key in settings, or I have to use another key, that works the same as dig. Can anybody help me here?

What would be the default button? I've tried using thr mouse, the roller on the mouse, all my normal move buttons, the crouch buttons, the prone button, and even hit all of the numbers. I get no response at all. I don't mind assigning a button to "dig" but there is no setting for "dig" in the controls.

The e/f buttons didn't work.

It's the only level when you have to dig through a tunnel. I've got Reznov with me as well.

if it says its unbound, that means there is no binding to dig. bind a key to dig and it will work.

It's the only level when you have to dig through a tunnel. I've got Reznov with me as well.

bubbabigsexy

For me it was the mellee button, I think it was V as default.

That's the problem. If there was a control setting for dig, I would have already set a button for it. But there's nothing in the settings that says dig, so I don't know what button to set. It's very frustrating. With all the black ops people out threre, hasn't anyone else had this problem?