A wind sock can be used to find out where the wind comes from and how strong it is. By knowing these two information, we can choose a suitable site for wind farming. Wind is the strongest at the top of the hill. When the wind meets the hill, it is pushed upwards and gains speed as it is compressed. That's why an ideal site for a wind turbine ia at the top of a hill. Not all hills are suitable wind farm sites. A good hill for wind turbines should gently slope to the top.