One of the best forearm training tools you could have might actually be in your tool shed! The sledgehammer. The closer you grip towards the head of the hammer, the "lighter" the weight will be. The further away...the heavier (haha...it's physics b*tch!). Wherever you grab it, the task is simple. Perform 10-20 of each of the 4 moves shown here (radial and ulnar deviation, pronation and supination). Finish it off with 10 spins to incorporate them all together and fry those forearms in a big way!