stacks exceed the initial buy-in limit. In casinos and public cardrooms, however, the use of cash is occasionally restricted or discouraged, so players often establish a small cache of chips called the "kitty", used to pay for such things. Players contribute a chip of lowest value towards the kitty when they win a pot, and it pays for expenses other than bets such as tipping the dealer as well as (where applicable) to pay for "rent" (formally known as time fees) and/or buying fresh decks of cards (while many public cardrooms include such costs in the "rake" or other fees, some charge separately for such things as playing cards and "rent"), and similar costs. At a casino, dealers who exchange cash for chips are expected to immediately secure any cash by placing it into a locked box near their station. This means that regardless of how chips are purchased, when cashing them in it is typically not possible to sell them back to the dealer since they have no access to any cash. Poker chips must therefore be taken to the cashier to be exchanged for cash. Dealers who handle buy-ins will often be willing (and sometimes encourage) departing players to "color up" their stacks by exchanging them for the highest-available denominations, both for the convenience of the player and to minimize the number of times casino staff must deliver fresh chips to the poker table - a time-consuming process. On the other hand, casinos that expect players to buy chips from the cashier will usually furnish players with chip trays (typically designed to handle 100 chips each) to ease the handling of large numbers of chips. Chips given by players or otherwise retained by the dealer for tips, rake and other fees (where applicable) are usually placed in separate locked boxes by the dealer, although in some casinos the rake is kept in a separate row in the dealer's tray. Other rules Public cardrooms often have additional rules designed to speed up play, earn revenue for the casino (such as the "rake"), improve security and discourage cheating. Forced bets All poker games require some forced bets to create an initial stake for the players to contest, as well as an initial cost of being dealt each hand for one or more players. The requirements for forced bets and the betting limits of the game (see below) are collectively called