Ground rule double?

Question
What is a layman's definition for the ground-rule double?  When does it apply?  How has it affected the game after it was added?

Answer
John,

A ground rule double is just what it says.  When the ground rules for the stadium say a struck ball should be scored a certain way, then the hit is a double regardless of how it is played by the fielder.

One example is that in certain domed stadiums, if a ball hits the roof, it is considered a double.  That is the ground rule in the stadium.  However, other domed stadiums may call a ball that hits the roof in play.  It depends on the ground rules in effect in that stadium.

Often, the term is used to describe a ball that bounces once and then goes into the stands.  However, that isn't really a ground rule double, because that rule is the same throughout all stadiums in baseball.

Hope this helps!

Brian