I would be remiss if I didn't mention that others don't always agree that these knives were ever allowed on ships. I personally think that the smaller types might have been allowed, if NOT on treasure ships or (strict) naval vessel, at least merchantmen and undoubtedly Privateers/pirate vessels. Gikkerson in particular lists numerous accounts of actual events involving clasps used for the wrong reasons. Hopefully, for the mot part, these knives led ordinary existences as a sailor's best tool. Many of them were flat at the end (no point), so they mot certainly could have doubled as shaving razors. Likewise, landlubbers such as soldiers, craftsmen, explorers, etc, would have found them most useful. It can also be said that Native Americans also sometimes traded in them and examples have been found/dug up at tribal sites. See 'Indian Trade Relics' by Lar Hothem for examples.
http://www.vikingsword.com/vb/showth...reasure+Fleets