Gambling is an attempt to win money by predicting the outcome of a race or competition. From the point of view of the gambler, it is a sure way to increase their financial wealth by outsmarting the bookmaker. From the point of view of the bookmaker, it is a sure way to increase their financial wealth by allowing gamblers into their betting shops, where they will outsmart themselves.

Most legal gambling in the United Kingdom is concerned with transactions recorded on small pieces of paper, which the gambler marks with the details of their prediction for any given event. After the event has passed, the bookmaker will momentarily glance at this piece of paper, and, in the vast majority of cases, will mark it with a big red pen indicating that the gambler's money, which the bookmaker was looking after at the time, is still being looked after, although any relationship it had with the gambler has ceased.

Occasionally, much to the surprise of the gambler (and the irritation of the bookmaker), the finely-honed skills of the gambler will pay off, enabling him to correctly identify a winning selection in advance of the event. This sort of thing can be financially embarrassing to the bookmaker, and consequently several precautions are taken to minimize this loss.

The most important of these precautions is tax. Tax is charged at a rate of nine percent of the gambler's financial contribution to the bookmaker. This is optional, however, and if the gambler chooses not to pay it when the transaction is initiated, and then finds that he has won, nine percent of his winnings are retained by the bookmaker. This is bad news for two reasons. Firstly, the bookmakers only pass on six and a quarter percent of the total stake to the government, keeping the remainder for themselves. Secondly, if the selection wins, the bookmaker still only pays six and a quarter percent of the stake to the government, but keeps the vast majority of the deduction for himself. On this basis, it is almost impossible for the bookmaker to lose money.

While that sounds like good news for bookmakers, they are faced with many hardships in their place of work. Most of these are caused by customers who, for no apparently logical reason, fill in their betting slip in what is apparently morse code, sanskrit, runic, or some other obscure writing system. There are also those who do not bother to write the time of the race that they are betting on, and, in extreme cases, neither write the time of the race, the amount they want to gamble, nor what they actually want to bet on. All of these problems contribute to delays in placing bets before the event has started, which translates into stress on the part of the staff and financial loss on the part of the management.

Many solutions have been suggested to this problem, one of which is 'mark sense cards'. Those wishing to place bets must make rudimentary marks on a pre-formatted machine-readable form to indicate the details of their bet. After reading these cards, the machine then prints out a legible summary of the bet placed. The name 'mark sense cards' is misleading, however, because the machines designed to read the marks on the cards either can't see a perfectly obvious mark, or can manage to detect a mark that would normally require a powerful electron microscope. The level of aggravation provided by these machines rises as the start-time of the event approaches, leading to even greater stress levels on the part of the operator.