Pull Down Hold using a Towel or Band
To do the Pull Down Hold, hold the band in both hands with your hands about hip-width apart. Slightly pull out on the band so that there is tension on the band or towel. Press your chest out and reach the band overhead, keeping the band/towel tight between your hands. You may need to adjust your hands in closer if the band is light. On a towel as long as you pull out with your hands about hip to shoulder-width you should be fine since it won’t stretch like the band. You want to pull out on it so your hands are not much wider than shoulder-width apart at most.
Then pull the band down toward your chest, as if pulling your chest up to the bar during a Pull Up. Pinch your shoulder blades down and back and feel your back working to pull the band down. Drive your elbows down to the ground and slightly back as you pull the band down keeping it tight between your hands.
Hold at this bottom position. Really press your chest out and engage your upper back as you hold. Do not lose tension as you hold. Do not arch your low back even though you want to press your chest out. Make sure you also don’t simply feel the outsides of your shoulders working, but instead feel your back. If you only feel your shoulders, you may be using too heavy a band or you may be too focused on pulling out on the band instead of down.