A hat is a head covering. It can be worn for protection against the elements, ceremonial reason, religious reasons, safety, or as a fashion accessory. In the past, hats were an indicator of social status. In the military, they may denote nationality, branch of service, rank and/or regiment. Some hats have a protective function. As examples, the hard hat protects construction workers' heads from injury by falling objects, a sun hat shades the face and shoulders from the sun, and a Ushanka fur hat with fold-down ear-flaps keeps the head warm. Some hats are worn for ceremonial purposes, such as the mortarboard, which is worn during graduation ceremonies. Some hats are worn by members of a certain profession, such as the Toque worn by chefs. Some hats have a religious functions, such as the turban worn by Sikhs.