Maybe BadTrainDriver needs a bike again - not sure where else the sandy folds are coming from. IANAL either, but that's what I heard from the couple of cop friends I talked to. Knife appearance, length and opening mechanism influence the cop's discretion. What you're doing at the time of discovery has a bearing on it, and yes, your own appearance and age can as well. I doubt a cop is going to slam compliant grandpa with a gentleman's folder against the ground unless grandpa is robb'n, kill'n and steal'n at the time. Conversely, an opinionated young punk with a spring-assisted 3" blade in a tacticool handle might have some 'splaining to do. Personally I prefer not to carry spring-assisted folders unless they're short like the smaller SOG Flash (which makes a great wire stripper for an electronics professional BTW). Even better if they have an engaged lock feature. Flippers are probably OK if they're well below the 3" mark. Anything bigger gets hung on the outside of my pants, and in all cases, if a cop "engages me," I'm going to take the first calm opportunity to politely inform him with hands clearly visible that I have a pocket knife in my front right pocket and then ask him how he wishes to proceed. Respect for his safety can go a long way in demonstrating benign intent. Again, IANAL and YMMV, but those are my thoughts. I really wish I could attend this training!