Boot knives, also called a gambler's dagger, is a small fixed-blade knife, usually a dagger, that is designed to be carried in or on a boot. Typically, such a knife is worn on a belt or under a pant leg. If worn around the neck (by means of a chain or lanyard) they become a neck knife. Boot knives generally come with a sheath that includes some form of a clip. Most have double-edged blades, like a dagger, that range from 3 to 5 inches.