File:Navaja Folding Knife, Circa 1790.jpg

English: Navajas are traditional Spanish folding knives. Though best know for fighting and personal defense, Navajas were used for everything from cutting lines, peeling fruit and shaving. They were even used to perform surgery. Over time a locking style blade with a backspring evolved. These knives were called Navaja de Muelles (Spring Knives). A metal pull ring to release the lock was added in the late 18th century. The ring was eventually discarded in favor of a lever. This style of Navaja is sometimes called a "tail rattler" (cola de crotalo), because the tip of the handle resembles a rattle snakes tail.