The verbal cue for ardha uttanasana often goes something like, "fingertips to the floor, come to a flat back." But what if those two instructions are mutually exclusive? The answer is to bring your fingertips off the floor and onto your legs. They may fall on the ankles, shins, or thighs (avoid pressing directly on the knees), whatever it takes to get the back flat. A mirror or a trusted friend can help you figure out approximately where you should place your hands so that you can avoid rounding the spine.