I am a police officer in NC. I hoped the following is helpful.
Nc G.S. § 14-269. Carrying concealed weapons
(a) It shall be unlawful for any person willfully and intentionally to carry concealed about his person any bowie knife, dirk, dagger, slung shot, loaded cane, metallic knuckles, razor, shurikin, stun gun, or other deadly weapon of like kind, except when the person is on the persons own premises
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A "pocket knife" is an exception to this.
North Carolina statute defines a pocket knife as a small knife, made to carry in a pocket or purse, which has its cutting edge and point entirely enclosed by the handle, and that may not be opened by a throwing, explosive, or spring action.
Fyi, if the clip is showing it is not technically concealed. So a spring assisted knife would be legally fine to carry as long as the clip is showing. "Switchblades" are legal to own and carry, just not carry concealed.
http://www.knifeup.com/north-carolina-knife-laws/ is a site that goes into more detail.