I figured out how to contact Drive. They call these things "Step Tubes", god knows why. The did explain you are to step on them when you come to a bump or small step and then press down on the handlebars to raise the front of the rollator aiding in going over the obstruction while preventing it from rolling backward. I tried it today and, I was surprised but, it really helps. They should explain this feature more thoroughly in the manual.
I wanted to come back and say how much I like and use this feature. It works great for me. I use it a lot. Anytime I come to a bump or small step-up the wheels won't roll over. I even use it for real steps that are singles -- i.e. not stairs.