I have observed three styles of clasp locks in navajas, however I do not know if they have any specific names.
They all share a similar backspring, a thick steel leafspring that is actualy external and is located on the back of the handle. They commonly run, from the base of blade, three quarters the length of the handle and it's full width. There are two "wings" on either side of the spring that wrap around the side of the handle and are riveted to it, typicaly in the uppermost half of their long handles, that serve as the fulcrum.
To disengage the lock, there are two main systems; the first is a ring attatched to the end of the backspring at the base of the blade, and the second is a lever-like mechanism with it's fulcrum at the base of the blade that you lift from the rear and pry the spring up with.
Of the three locking mechanisms, one is akin to a lockback, one similar to a ratchet, and the third, and what appears to be the strongest, is a modified version of the ratchet-style.
The lockback-like mechanism has the end of it's backspring bent at aproximately 90 degrees, and engages a slot in the tang of the blade.
The ratchet-like mechanism has gearteeth on it's rounded tang, angle to allow opening but not closing, and the last is squared off to act as a bladestop. The teeth stick up through a hole in the backspring.
The modified ratchet-like mechanism has only a few gearteeth, two or four are the most common, but rather than being on the rounded tang they actualy sit atop a rectangular protrusion from the tang. The teeth are engaged by the backspring as in the ratchet-like lock, but the squared off end of the tang protrusion butts up against the handle when fully opened, thus acting as a backstop.
The reason I feel this is the strongest mechanism of the three is because the bladestop does not rely on the backspring to keep the blade from over-opening. On the other two, pressure forcing the blade backward will put strain on the spring in such a way that it will cause it to flex, weakening and potentialy disengaging the lock. Because we're talking about a thick backspring, we're talking a lot of force, but on the modified-ratchet there is no pressure on the backspring to keep the blade from over-opening, and the teeth of the ratchet are angled in such a way that to any force applied trying to close the blade without disengaging the mechanism with only draw the spring tighter against the teeth.
NOTE:Both clasplocks and navajas are extremely old paterns. The earliest uncontested reference to navajas dates to 1490, in Alfonso Fernandez de Palencia's Universal Vocabulario en Latin y en Romance, and there are other posible mention of these style of knives going back to the 14th or even 13th century. There have been countless variations in the figure of both the navaja and it's lock, as well as in clasp locks in general, and all are executed with varying degrees of quality and ingenuity.
Another early lock that I have no name for whatsoever consist of merely a long section of the tang that fits into a groove in the back of the handle when open and is held in place by the presure of the palm againgst the handle. Another one that shrugs off white-knucke-tests, even if it does not make for as compact a folder as the modern locks do.
Many of these early locks are quite strong as they were often placed on large knives,navajas are not uncommonly three feet when open, the biggest on record was 4.5 feet. Yes, they used them when they were that big. My kinda people
. Also, many of these knives saw double-duty as weapons.
As weapons they were universaly disdained by nobility, who favored the sword and pistol, these knives were the mainstay of the working class and peasantry right up through the 19th century and continue to see use by rural Hispanics in many nations as well as amongst the Romani.
