The arms hold the tubular hoop perfectly square with the work surface and directly over the lower ring.  All you have to do is align the shirt and press the hoop down. The arms actually hold the hoop directly over the lower ring and square with the Station.

With the Fixture arms holding the hoop for you, it allows you to concentrate more on the shirt and the actual placement of the logo. This speeds the hooping process and makes it much more accurate.