Most case law I have read on the matter suggests that the object must be clearly identifiable as a knife by a casual observer. It is worth noting that many cases suggest that a knife carried in a way that a cop can pick out, but a civilian would miss entirely, still counts as concealed because cops are "specially trained" to identify weapons. Pocket clip showing is a huge gray area (though only really applicable to folders) and I would never trust it as any sort of standard. Some cases have ruled a visible pocket clip as concealed because the body of the knife was so hidden it was not identifiable as a knife to a non-trained person. On the other hand, pocket clips are routinely used in New York cases as unlawful open carry (open carry is not permitted in NYC, but concealed is).
