First the easy & "normal" one.
The way I like it. Probably the most secure. It doesn't use the keeper at all. This can be done two ways, but the picture would be the same. The strap can go around the pivot both directions. If you go "in" on the far side of the pivot before coming back out under the original strap, it is very difficult to thread the buckle.
The same arrangement but with the strap loose so you can see its path.
Instead of using the pivot as a keeper before being threaded back this combination uses the normal keeper.
This threading pattern uses the pivot instead of the keeper. The strap is quite loose so that you can see how it is threaded.
This threading pattern is just more work than useful. The strap comes in to the buckle the "normal" way, loops under the pivot pin, then through the keeper, and finally, back out the way it came in.
The jacket also has a cloth keeper past the buckle. For completeness here is a picture of it.
This picture shows a "Posey Clip". It clips on to the strap after it passes through the buckle. It makes it a bit harder to get a buckle undone. I don't think Posey makes them any more.
Thanks Yossie, for hosting my page at blacksteel.com