A rack is the plastic tray used to hold and carry casino chips. The standard player rack has five grooves and holds 100 chips, 20 to a row, which makes it easy to count a stack at a glance and keep denominations apart. Racks are usually made of clear or translucent plastic, so staff can see what is inside and nothing can be hidden underneath. When a player leaves a table with a large stack, the dealer offers a rack so the chips can be carried to the cage.
The tray of chips in front of the dealer is also called the rack or chip tray, and its contents are tracked through fills and credits. Online there is no physical rack, but the same idea of a clear, countable balance applies to the player’s wallet display and the operator’s cash reconciliation.