In California, it's legal to carry a folding knife concealed. Open carrying a folding knife would be unusual here, and I personally have never seen anybody do that. You must carry a
fixed blade open (e.g., knife sheath on belt).
http://www.shouselaw.com/california-knife-laws.htmlI carry my locking folder (BM 940 or 710 depending) clipped to my right front pocket so that it is visible and not concealed.
If the knife is inside the pocket with the clip outside, then that's considered concealed, especially if your shirt falls over the knife at any time. By the way, when I'm confused about what's legal, I prefer to consult a lawyer, not a police officer.