Attach a weight to one end of a rope or bar. Hold the other end of the rope or bar with both hands, palms facing down. Stand with your feet shoulder-width apart and your arms fully extended in front of you. Slowly roll the weight up towards your hands by flexing your wrists. Pause for a moment at the top, then slowly lower the weight back down to the starting position. Repeat for the desired number of repetitions.
GIF