Each deal is held in a board with four pockets, one per hand (Law 2); The board designates the dealer and which side is vulnerable, so every table plays the deal under identical conditions; Boards are numbered, letting the same deal be compared across the whole field
Why people argue about this
People often assume that the numbering of boards is just for keeping track of which deal has been played where, but they overlook how crucial it is in ensuring fairness across all tables - without board numbers, deals could be swapped between tables, completely undermining the concept of identical conditions and vulnerability designations.
