I use one all the time. I have been doing BOMs and sometimes the directions call for a seam to be pressed open at bulky intersections.
What my hubby did was cut an 18" piece of handrail for me. While it is already flat on one side, he actually took off about 1" because he thought it would be more stable. I use it just as is - no covering. It allows me to press one seam and not disturb others.