Yes. Knives are an important tool to have on hand. They're convenient when working on deck, but they're also an important safety tool. Sailors carry knives in case they need to cut a line quickly to release a jam that will break something, or worse still, to get themselves out of a tangle or entrapment situation. For this reason, it is a requirement on many offshore yachts that there be a knife mounted in the cockpit, and each person carries their own, as well.