Might be a stupid question. But I have to replace one of the bolts of the factory grounding points. When I was installing grounding wires, the bolt wouldn't screw back because it was quite rusted. Picture from a thread in myg37 is shown below.

It is the middle bolt. I'll go to the hardware store tomorrow with the one I have. But it'd be nice if someone knew exactly what kind of bolt it was. Thanks!

 

Well, if you want to leave both your grounding wires on why don't you put one bolt for 2 wires? That's what i did.

 

Tried that. But I can't get all four wires on one bolt, well at least not the other one. It's too short.