I have been looking for something like this, and am so glad I found it.  It allows  your hand luggage to be strapped securely to the handles of your wheeled suitcase, without twisting or slipping.  It was a real lifesaver when I had to drag all my luggage through various train stations and on/off trains in Tokyo last spring.  The resultant bag was heavy but manageable, and I was even able to wrap around my travel pillow, jacket, and snack bag as well as my carryon.  Independent travel always presents unexpected luggage transfer issues--stairs, inter-station hikes, buses with no luggage racks, etc.  In enabling many items to be condensed into one, this is one travel "help" that makes dealing with the unexpected a little easier.