This package includes the parts to make a buckle. You can use it for a belt with nylon 1 inch webbing or a luggage strap.
These parts were not designed by me. I only fixed the model errors and added tree support to the female buckle via MeshMixer.
Warning: Don't force the buckle to fit in the wrong direction. Flip it over if it doesn't fit.
Tree female should be printable without support.