How do I remove a cap that doesn't unscrew?

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I tried to unscrew these caps but they just turn. I assume they are caps but don't want to damage them so I was looking for someone to verify how to remove the 4 caps in the photo. Thanks

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do you mean the acorn nuts? try holding the one opposite from where you are turning.

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you can try lifting from the back side of the cap as you turn it this may help it grab the threads

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This is like trying to ID a robber from a surveillance camera. How about a close up of the nut?

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