To protect himself in such case the banker would, at the time he sent over the commercial exchange, sell his own demand drafts for future delivery. Suppose that he had sent over £25,000 of commercial "payment" bills. Unable to tell exactly when the proceeds would become available, the banker buying the bills would nevertheless presumably have had experience with bills of the same name before and would be able to form a pretty accurate estimate as to when the drawees would be likely to "take them up" under rebate. It would be reasonably safe, for instance, for the banker to sell futures as follows: £5,000 deliverable in fifteen days; £10,000 deliverable in thirty days, £10,000 deliverable in from forty-five to sixty days. Such drafts on being presented could in all probability be taken care of out of the prepayments on the commercial bills. By figuring with judgment, foreign exchange bankers are often able to make substantial profits on operations of this kind. An exchange broker comes in and offers a banker here a lot of good "payment" commercial bills. The banker finds that he can sell his own draft for delivery at about the time the commercial drafts are apt to be paid under rebate, at a price which means a good net profit. The operation ties up capital, it is true, but is without risk. Not infrequently good commercial "payment" bills can be bought at such a price and bankers' futures sold against them at such a price that there is a substantial profit to be made. The other operation is the sale of bankers' futures, not against remittances of actual commercial exchange but against exporters' futures. Exporters of merchandise frequently quote prices to customers abroad for shipment to be made in some following month, to establish which fixed price the exporter has to fix a rate of exchange definitely with some banker. "I am going to ship so-and-so so many tubs of lard next May," says the exporter to the banker, "the drafts against them will amount to so-and-so-much. What rate will you pay me for them--delivery next May?" The banker knows he can sell his own draft for May delivery for, say, 4.87. He bids the exporter 4.86-1/2 for his lard bills, and gets the contract. Without any risk and without tying up a dollar of capital the banker has made one-half cent per pound sterling on the whole amount of the shipment. In May, the lard bills will come in to him, and he will pay for them at a rate of 4.86-1/2, turning around and delivering his own draft against them at 4.87. Selling futures against futures is not the easiest form of foreign exchange business to put through, but when a house has a large number of commercial exporters among its clients there are generally to be found among them some who want to sell their exchange for future delivery. As to the buyer of the banker's "future," such a buyer might be, for instance, another banker who had sold finance-bills and wants to limit the cost of "covering" them.