It rather depends on the patent claims. There are over 500 patents on barbed wire, and searching for "paper clip" just now, there are new paper clip patents in the last few years, like 6,973,700 and 7,500,301. To say nothing of the many design patents for paper clips.

So not, it's not obvious that it will be rejected. It could be a seemingly minor thing. I brought up paperclips because in Henry Petroski's "The Evolution of Useful Things", the author describes how one paperclip patent claim was for the variant where the outside wire extends beyond the loop of the paperclip. That seems like a minor variation, but the submitter showed that no one else had done it, and got the patent.