Page "Slot machine" Paragraph 89

Many American casinos offer free memberships in " slot clubs ," which return a fraction of the amount of money that is bet in the form of comps ( complimentary food, drinks, hotel rooms, or merchandise ), or sometimes as cash or a promise to pay cash at a later date.

These clubs require that players use cards that are inserted into the slot machines, to allow the casinos to track the players ' " action " ( how much each player bets and for how long ), which is often used to establish levels of play that may make players eligible for additional comps.