The CQC-4K is a manual opener using either the thumb disk or the patented Emerson "wave shaped feature." This opening feature enables the knife to be opened as it is removed from the pocket. By the time the knife has been fully withdrawn from the pocket, the blade is deployed and ready for use. A small wave-shaped tab on the top of the blade is built to catch on the pocket seam, opening the knife as it comes out of the pocket. This instant-open feature is a favorite among military, rescue, and law enforcement knife users.