The closure is the most understated yet the most instrumental element of a wrist watch. Without a closure, in fact, a traditional wristwatch cannot be secured to the wrist - with the exception of bangle watches. Despite this key function only few people pay attention to it and only few watchmakers focus on this element to express their creativity.
Wristwatch closures can be classified mainly into two classes: clasp and buckle closures. Clasps are generally used on bracelets made of rigid material (e.g. metal, ceramic...) though lately they been used also for straps made of soft materials (e.g. leather, canvas…). On the other hand buckles, because their intrinsic structure, are used only on straps made of soft materials.
The following sections underline the different types of claps and buckles.
The so called claps closure is made of rigid materials (e.g. metal) and allows the functioning via the use of a series of hinges and folding elements. Generally the claps have three folding elements centered or sequential and more seldom two elements like in the jewelry clasp.
A deployment clasp, also known as fold-over-clasp, is the most basic kind of closure. It typically unfolds into thirds to allow the watch to fit over the wrist. It locks in place with a small pressure tab. The clasp has several holes in one of the three elements that can be used to adjust the bracelet circumference dimension without the need to add/remove links.
Due to the nature of the closing mechanism and the physical properties of the metals generally used, the pressure tab tends to wear out over time and the clasp might no longer operate properly. For this reason there exist some variants of the deployment clasp that aim at better securing the closure.
The most commonly used improvement is a flap that folds over the closed end of the clasp hence makes the clasp more difficult to open unintentionally – this is generally called “safety” deployment clasp or fold over clasp. A bit more sophisticated is the push-button deployment clasp in which the extra security is ensured via a locking mechanism that in order to be released needs the wearer to push one or two buttons generally located on the side of the closure. The two buttons are most of the time very visible but in certain cases they are integrated within the closure itself. Finally the safety clasp can be combined with the push-button clasp for the ultimate safety closure feature – this is the so called triple lock deployment clasp.
Butterfly and Jewelry Clasp
The typical deployment clasp is very noticeable and breaks the continuity of the bracelet. For this reason Louis Cartier invented the butterfly closure (ca 1910) which is invisible when closed and creates the illusion of a seamless band. This closure is still made of three folding elements, but differently from the typical deployment clasp in this closure there are two elements that fold symmetrically toward the middle from opposite ends of the clasp on top of a center element like the wings of a butterfly. Some butterfly deployment clasps have pushbutton release mechanisms for added security.
The jewelry clasp addresses a similar need via making the closure more elegant. This is the simplest closure and it is operated by a latch that snaps closed around a bar. It is released by lifting the clasp and unsnapping it from the latch bar.
The more traditional buckle is one of the oldest fastening devices. In particular, this is an adjustable closure made up of a pin (or prong) and frame system secured to one side of a band that combined with a series of holes on the other side of the band can help fastening the wristwatch.
The traditional buckle offers the convenience of an easy to adjust length of the bracelet however it is not that convenient in opening and closing. For this reason the folding clasp mechanism has been combined with the buckle system in the so called deployment buckles. Those can have the classic deployment clasp or the butterfly clasp opening mechanism but in both cases the combination with a typical buckle gives the flexibility to easily change the circumference to the strap and also the possibility to use on a traditional leather or canvas strap.
There are also other types of less common closures like the magnetic ones used on some Apple watch bracelet as well as variations of the above closures like the fliplock extension on the Rolex clasp to allow divers to easily adjust the bracelet for use above the dive-suit. However, the above should be representative of the bulk of closures currently used in the market.