Wearing a NATO Strap
For a first time wearer, a NATO strap can seem a little confusing. The straps were purposely designed to be long, so the excess tail of the strap could be doubled back and tucked into the keepers a second time.
The beauty in this design is the strap is "one size fits most." Small to medium-large wrists can tuck back the excess. Large wrists might not have enough excess to tuck back, but that's okay as well, as the strap tip will terminate close to the second keeper in this case.
Step by Step
Slide the long end of the strap through the buckle, and secure the buckle using the appropriate sizing hole on the strap.
Next, pass the "tail" of the strap upwards through both of the keepers. For most wrist sizes, there will be excess strap sticking upwards. We'll get to that in the next step.
The last step is to take that excess bit of strap tail, and fold it backwards into the keeper a second time. This step will hold the tail of the strap tucked in neat and tidy.
You can tuck the tip of the strap in either direction (outwards as pictured above, or inwards as pictured here). Tucking inward is a cleaner look, but this may not work for very small wrists.