The Dead Ground Rule in Article 9 says that “The jack is dead … when an out-of-bounds area [terrain interdit, dead ground] is situated between the jack and the throwing circle.” What does “between the jack and the throwing circle” mean?
Consider this diagram. (Note that it is not drawn to scale.) A game is being played on an L-shaped terrain. The jack has been knocked to a place where it is almost, but not completely, “around the corner” from the circle. Or, to put it another way, an area of dead ground is protruding into the terrain; it may possibly be blocking the line of play between the circle and the jack.
The players are uncertain what to do; they are asking questions: Is the jack alive or dead? Is there dead ground between jack and the circle?
What does “between the jack and the circle” mean?
The answer is that “between the jack and the circle” means “between the jack and any part of the circle”.
Suppose you draw lines from the jack to all of the parts of the circle, as in this diagram. If any of those lines crosses dead ground, then there is dead ground between the jack and the circle, and the jack is dead.
Mike Pegg described the rule this way on “Ask the Umpire”.
Imagine two lines extending from the two sides of the circle to the jack. If there is any dead ground between those two lines, the jack is dead.
Visual inspection should be enough to resolve the situation, but if it isn’t, you can take a long tape measure and pull it tight between the jack and various random points on the circle. If in any of those positions the tape crosses dead ground, there is dead ground between the jack and the circle, and the jack is dead.
The Rules of Petanque 