A prime, also called a wall, is a row of consecutive points that you hold with two or more checkers, forming a barrier your opponent cannot jump over. Because a checker can move at most six points on a single die, a full prime of six points in a row completely traps any enemy checker behind it. Even a partial four or five-point wall is very effective at slowing the opponent down. Building a prime in front of an enemy checker, especially one you have just hit, is one of the strongest strategies in backgammon. You gradually make points to extend the wall while keeping your own checkers safe.