Post security sales seem to have no relationship to TSA rules. Several years ago, in the zero tollerance for pointy objects era, when little folding nail files on clippers were getting confiscated by the ton everywhere, in an airside gift shop I think in EWR I saw a magic kit for kids which included several of those interlocking objects that you can only get apart if you know the secret. Except these puzzles were made from real 16 penny common nails, points and all. I'd be worried about a free trip to Gitmo if I tried to bring such an object thru the checkpoint, yet here they sell them in the "sterile" area.