Hold a barbell with a supinated grip and sit into a squat above parallel and rest your forearms on your thighs with the wrists in front of the knees.
 
Allow your wrists to extend, then curl the bar back up as far as possible. You can allow the fingers to extend in the bottom as well to include finger flexor work directly.
 
Purpose
The barbell wrist curl strengthens the wrist and improves grip strength by helping support a better hand position when holding a bar.
 
Programming
Generally sets of 10-30 are appropriate.