The end with the brass fitting is fitted to the tank end. The pictures of
the Bus-Depot reg have the fitting already on the reg and this implies (to
me) that it is included with the purchase of the reg and is screwed onto
the appropriate end. DO NOT connect this directly to the tank or the brass
fitting will break! Instead, just use good hose for a propane application,
thus isolating it from the jolting and vibration it would see if connected
directly to tank.
The end you see with the brass fitting is the propane inlet.

Once again, make sure that you mount it inside a protective box!
Forewarned is forearmed