Corked bat

From BR Bullpen

A corked bat is a bat that has been modified by hollowing a tube in the middle of the barrel and replacing the wood by a lighter substance such as cork or rubber balls. A corked bat is illegal, as a legal bat must be made from one solid piece of wood.

The theory behind a corked bat is that the modification allows the batter to swing a larger bat for a lighter weight, allowing for a faster - and thus more powerful - swing. There is doubt about how much this effect is truly worth, however batters have attempted to modify bats illegally for decades, and sometimes get caught. Graig Nettles, Sammy Sosa, Albert Belle and Chris Sabo are among players who were publicly caught when a modified bat they were using broke, revealing the cheating. Norm Cash claimed after he retired that he used a corked bat for most of his career, but was never caught. Allegations were also made that Pete Rose had used such bats for most of his career, but again no one had ever checked, in this case because he was a singles hitter, and that illegal bats tend to be associated with sluggers.