State laws do not, in my experience, clearly explain what "concealed" means in their statutory laws. Often the details of such matters is decided in appeals court opinions. However, I generally advise using the most cautious definition. If you and I are having a conversation on the street, I should be able to see that you have a knife, and also recognize that it is a knife and not, say, a pen or screwdriver. Assume in this instance I am neither a cop (who are trained to spot weapons) or a knife enthusiast (who knows what a pocket clip is). If your body is turned a certain way were I can't see it, that is not concealed, but if I cannot see and recognize it from any side of you, it is concealed.