When a player is first allocated a number, the numbers used correspond to their primary position. For example, if a player is assigned the number 10, then he or she is a left guard. If a player is assigned the number 93, then he or she is a wide receiver. However, players can change positions during their career. A player who starts out as a cornerback but later moves to safety would switch out his or her numbers with those of a player at the other end of the field (for example, from corner to field goal kicker). This is why it's important to look at a player's roster spot on your team when determining his or her number. For example, let's say that player A has been assigned the number 30 and player B has been assigned the number 92. A guards left while B goes right. Now, both A and B are guards and they will be given numbers in the 40s or 50s. They cannot change this fact by switching positions again after they have been assigned numbers. Players are also allowed to use their name as their uniform number. For example, quarterback Troy Davis could choose to wear number 4 because it was the number he wore at Arkansas.