Corking wooden baseball bats is a trick that has popped up from time to time in leagues that use wood bats, even as far up as Major League Baseball. However, one thing many people don't know is that an aluminum bat also can be corked. By taking the top off the bat and putting tennis balls inside the barrel, the bat's bounce power will increase dramatically, which could mean the difference between a home run and a fly out.
Pry the flat-head screwdriver under the cap on top of the bat's barrel. It may take some muscle, but it will pop off. There will be a large popping sound as the pressurized barrel's air escapes.
Push tennis balls down into the barrel. Depending on the size of the bat, three of four tennis balls will fit inside the barrel.
Place the cap back on the bat and push it in until it is secure.