You may be referring to a position podiatrists call the Windless mechanism. This static position can also be used to stretch the plantar fascia. The plantar fascia is located along the bottom of the foot.
Sitting in a chair, cross your affected leg over your other leg. The painful foot and ankle are resting on the thigh just above your knee. Pull your toes toward the shin. Stop pulling the toes upward when you will feel the stretch, tension, and discomfort or pain.
Hold the stretch for at least 10 seconds. Repeat 10 times. This exercise can be done any time throughout the day. It is especially helpful when done right before getting out of bed or before standing up after sitting for a long time.
There is evidence from one study suggesting that results after eight weeks of stretching in this way are very positive. Patients had less pain and increased function. Improvements were still present when patients were contacted two years later.