Oh I get you now! I wondered why you were being so vague about it, but now I know which bit you mean haha
I had to do the same though, hammer and a punch to get them lose and then mole grips or plumbers plyers to turn them. I think you can get the correct tool though somewhere. Clean up the threads once you get them off with a wire brush and penetrative spray then probably put new ones on to prevent it happening again.
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