If a watch is provided with a folding clasp, there is a closure by means of two hinged metal strips which are attached to the strap of the watch and which are bent in the shape of the wrist.
Because this closure is foldable, the watch can be put around the wrist like a bracelet and then, when closing, it folds one metal strip over the other metal strip. A folding clasp is often more expensive than a tang buckle, but with a folding clasp your watch strap will last longer. Moreover, the chance that your luxury watch falls of your wrist, when putting on or taking off, is smaller.