There are a metal rod and plastic knobs that you turn to tighten it against your door frame. It's super easy to tighten and loosen in order to adjust the height of your Mobility Wall, depending on which part of your body you want to target.
The actual foam-roller part is made with EVA foam, which is firm yet soft, and I love that it's split into two foam rollers to leave space for your spine. It's lightweight, too, weighting just 10.2 pounds.