Let us assume that you have 1000 GPB, and the exchange rate of GBPUSD is 1.6000. You sell your GBP for 1600 USD and you hope that GBP falls against USD. After a while, the rate falls up to 1.5900, and you decide to make a reverse operation and buy GBP for 1600 USD at this rate. As a result, you have 1006.28 GPB. This way, you have fixed a profit of 6.28 GPB.We can make several conclusions based on these examples