The purpose of the dealer button is to rotate the blinds and positions fairly among all players. After each hand, the button moves one position clockwise to the next player. This ensures that every player gets the opportunity to play from each position and contributes the same amount in blinds over the course of a full rotation.
A "fixed button" (or "dead button") occurs when a player's departure or elimination would disrupt the blind rotation, creating an unfair scenario. The button remains in its current position for one hand to re-establish the correct order.
The Specific Scenario: This rule is almost exclusively used when the player who is next in line to receive the button is eliminated or leaves the table. The rule is in place to prevent a player from being forced to post the big blind in two consecutive hands.
Example:
Previous Hand: Player A is the button, Player B is the Small Blind, Player C is the Big Blind, and Player D is first to act or UTG.
Hand's End: The hand plays out and Player B is eliminated.
The Problem: In the next hand, the button is supposed to move to Player B, but this player is no longer at the table. If it were to move all the way to Player C (the next active player), Players C and D would get to skip paying the Small Blind and Big Blind respectively. This is unfair.
The Solution: To fix this, the button remains on Player A. The small blind moves correctly to Player C and the Big Blind is posted by Player D.
Result: After this single hand with a fixed button, the rotation is back in order. The button will then move clockwise as usual in the following hand, and every player will be back in the correct blind rotation.
This rule is a crucial part of tournament etiquette and fairness. It ensures that the blinds are paid correctly and that no player is at an unfair disadvantage due to another player's departure.