A vane is an object used to measure the direction of the wind. The most common type of vane is a FAN, which has three blades that spin in the wind and point in the direction of the wind. A WEATHERCOCK is another type of vane, which is usually a rooster-shaped object mounted on a pole and used to indicate the direction of the wind. Finally, a sail on a windmill is also a type of vane, as it is designed to catch the wind and turn the windmill's blades.