I'm trying to finish installing new ball joints. The old ones had torx fittings on the ends of the studs to hold it still while tightening/loosening the nut. The new ones do not have the torx fitting. I was able to tighten the driver's side without it and (apparently) without turning the stud. However, on the passenger's side, the stud turns and the nut doesn't tighten. How do I tighten that one?

 

You can put a jack under the control arm and put some pressure on it. Then try to tighten it.