Urgent: Need help installing tie rod? on w124...

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Hey everyone. I am trying to replace the tie rod? on the rear passenger side of my 92 300e. Partsshop calls it a thrust arm link and quite frankly I don't know what its really called. Its purpose seems to be to keep the back tire straight, and not pointing to the left or the right. I know this because I bent it and my back passenger-side wheel was pointing towards the drivers seat.

I can't seem to tighten this part down. The bolt that connects to the wheel hub keeps on turning when I try to tighten the nut on it. The arm is sealed at this end so I can't stabalize it with anything. What can I do to keep the bolt from spinning so I can tighten it into place? Thanks!