There are many things to consider when choosing a knife to carry. Important features are the  knife's quality, design, and legal compliance. The design of the knife is probably the most important factor. Good ones are made from tough steels, have sturdy handles and reliable mechanisms. Need a knife fast? Stop fumbling around in your pocket, it's right on your belt buckle and it'll come out with the flick of a thumb. No messing around to try to find a knife. It's always right where you need it. A flick of the thumb and it's open and ready to go.