The wonderful world of watch straps — leather, rubber, NATO or otherwise — is endlessly varied. Though many types defy classification, it’s helpful to know some common terms and varieties related to that essential part of any band, bracelet or strap: its buckle or clasp — in other words, the hardware that helps you actually affix a watch to your wrist.
Most fastening methods can broadly be broken into two varieties: the buckle and the clasp. There’s more or less one kind of buckle, but there are several kinds of clasps each of which can also have variations associated with it. Though often overlooked, the features, comfort and quality of this hardware can factor into the value of a watch. Here are the important terms and types you need to know:
Pin / Ardillon / Tang Buckle

You can probably just call this style a “buckle” without any confusion, but you’ll see it referred to as “pin buckle” (relatively intuitive) as well as “ardillon” and “tang.” What you need to know is that all these names are referring to the same simple system which essentially functions like most belts that hold up your pants. They can come in all kinds of shapes, finishes, materials and sizes, but they generally feature a bar, a frame and a pin which goes in the holes on the strap’s other end. The remaining length is tucked into the keepers.
Keeper: The loops, usually of fabric, leather or metal, which keep the long end of the strap from flapping around. Most straps have two, but some feature only one keeper.