The picture below shows an example of a 6GR test position. The restriction ring adds difficulty similar to that which would be encountered welding a butt joint on a T, K, or Y connection. Click on the picture to see it full size. Other positions can be seen in the other thumbnails.
A 6G test is done out in the open usually. The picture below is a SS GTAW root with the remainder filled and capped with SMAW (Stick E309-16) . This was a test for the boilermakers. My cell phone isn't much for up close photography.