Support your forearm on a bench or box, on your knees, or stand with the arms raised to about 45 degrees, and hold a small plate in the hand with the thumb on top. Keeping the wrist and forearm aligned, use a controlled speed to move the weight as far down as possible, and then as far up as possible.
 
Purpose
The wrist radial deviation is a simple exercise to strengthen the wrist; it should be combined with ulnar deviation.
 
Programming
Generally sets of 8-15 reps are appropriate.