Corked bat

In baseball, a corked bat is a specially modified baseball bat[?] that has been filled with cork or similar light but dense substances to make the bat lighter without losing much power. A lighter bat gives a hitter a quicker swing and may improve the hitter's timing. Since the bat is lighter, the ball does not necessarily travel as far as with a heavier bat, but usually only by a few feet at most. In Major League Baseball, modifying a bat with foreign substances and using it in play is illegal and subject to ejection and further punishment.

To modify a wooden bat to a corked bat, a hole approximately 1/2-inch in diameter is drilled down through the thick end of the bat roughly six inches deep. Crushed cork, super ball[?], sawdust, or other similar material is compacted into the hole and the end is typically patched up with glue and sawdust. Placing cork beyond roughly six inches into the bat threatens the bat's structural integrity and makes it more susceptible to breakage. Corked bats breaking while in play during games is the most typical way that their use is discovered.

Using a corked bat in Major League Baseball is in violation of Rule 6.06 (d), which reads in full:

A batter is out for illegal action when:

(d) He uses or attempts to use a bat that, in the umpire's judgment, has been altered or tampered with in such a way to improve the distance factor or cause an unusual reaction on the baseball. This includes, bats that are filled, flat surfaced, nailed, hollowed, grooved or covered with a substance such as paraffin, wax, etc. No advancement on the bases will be allowed and any out or outs made during a play shall stand. In addition to being called out, the player shall be ejected from the game and may be subject to additional penalties as determined by his League President.