Apple Watch 3 - Leather straps

There are different band closures, each with their own mechanism.

Pin closure
Secure the band by pushing the pin into the correct hole. Fold away the remainder.

Buckle closure
Adjust by inserting the pin through the correct hole and secure with the buckle.

G-hook closure
Adjust by securing the metal G-hook in the desired position.

Magnetic closure
Adjust using the magnets at the ends of the band.

Butterfly closure
Fold the two hinges together to click closed and press the buttons on the sides to open. (Not adjustable)

Fold closure
Thread the band through the closure and click secure with the buckle. Open by unfolding the closure.

No closure
One size, not adjustable.