Hi jerrygirl and thanks for your question. These units are 4-wheeled units, as you pointed out. Some have an integral lip to be able to grasp by the hand. That makes it somewhat more manageable to move throughout the house. However, it is a real challenge to try to use those wheels to move them outside, as when you're traveling. I'm not sure the wheels are even designed for outside use. You may want to contact the manufacturer to see if they can suggest something.
All the best,
Leon (site moderator)