Summarize the following:
Start the exercise by lying down, extending your legs, and pointing your toes upward to form a straight line with your body. Relax your shoulders and neck and find a comfortable position. Use a yoga mat, a towel, or work on a carpeted or padded floor to make the exercise more comfortable. Interlace or stack your fingers and place them behind your neck to help support your head during the exercise. Your hands should rest comfortably behind your neck and shouldn’t pull on your head.  Don’t round your neck and spine. If you have shoulder flexibility or mobility issues, you can place your fingertips on the sides of your head. Keep your legs together and extend them so they’re straight. You can bend your knees slightly if your flexibility doesn’t allow you to keep them straight, but work to straighten your legs out over time.  Try doing yoga to stretch your hamstrings to improve the flexibility of your legs. You can cross your ankles if it makes it more comfortable for you. Once you’re in a good position with your legs elevated, take a breath and brace your core for the movement by contracting and keeping it tight. Keep your back fully connected to the ground. There should not be any space between your lower back and the ground.

Summary:
Lie flat on your back on the ground. Fold your hands and place them behind your neck. Raise both of your legs so they’re perpendicular to the ground. Contract your core to prepare for the movement.