OE running board nut size?

I’m trying to put a socket on the nut to loosen them. I’ve concluded that it’s a 9/16 deep well. I was expecting a bolt head, but it appears to me that they have welded threaded rods onto the frame and the running board support brackets are attached by nuts which thread onto these rods. Should I be looking for two pieces of hardware? As in a removable bolt and nut? From what I see, if I’m successful, is a left over threaded rod remaining after the nuts and running boards are removed. Am I correct?


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