1) The apparatus is hinged at the elbow. It is a literal "hitting machine" that allows Bonds to release his front arm on the same plane during every swing. It largely accounts for the seemingly magical consistency of every Bonds stroke.
2) The apparatus locks at the elbow when the lead arm is fully elongated because of a small flap at the top of the bottom section that fits into a groove in the bottom of the top section. The locked arm forms a rigid front arm fulcrum that allows extraordinary, maximally efficient explosion of the levers of Bonds' wrists. Bonds hands are quicker than those of average hitters because of his mechanical "assistant."
3) When Bonds swings, the weight of the apparatus helps to seal his inner upper arm to his torso at impact. Thus "connected," he automatically hits the ball with the weight of his entire body - not just his arms - as average hitters ("extending") tend to do.
4) Bonds has performed less well in Home Run Derbies than one might expect because he has no excuse to wear a "protector" facing a batting practice pitcher. As he tires, his front arm elbow tends to lift and he swings under the ball, producing towering pop flies or topspin liners that stay in the park. When the apparatus is worn, its weight keeps his elbow down and he drives the ball with backspin.
5) Bonds enjoys quicker access to the inside pitch than average hitters because his "assistant" - counter-intuitively - allows him to turn more rapidly. Everyone understands that skaters accelerate their spins by pulling their arms into their torsos, closer to their axes of rotation. When Bonds is confronted with an inside pitch, he spins like a skater because his upper front arm is "assistant"-sealed tightly against the side of his chest.
6) At impact, Bonds has additional mass (the weight of his "assistant") not available to the average hitter. The combined weight of "assistant" and bat is probably equal to the weight of the lumber wielded by Babe Ruth but with more manageable weight distribution.