Deck is used to signify or specify the number of open orders that a stockbroker is working on at any given point in time and is also commonly known as a broker’s deck. A broker’s deck is not only limited to stock that they buy and sell but is extended to any security that they deal with like currency, commodities, derivatives, etc.
Trading firms or units further have individual traders or brokers that cater to the clients or customers that they have secured or the portfolios that they are responsible for.
A broker with a larger deck implies that such a broker is responsible for many portfolios and their performance. However, with the increased dependency on technology for trading, brokers may also face difficulties in handling a huge volume of portfolios in the case of any technological breakdown.