Launched in the 1940s by the Shirley Institute, the Shirley Togmeter is the standard apparatus for rating thermal resistance of textiles, commonly known as the Tog Test. This apparatus, described in BS 4745:2005 measures a sample of textile, either between two metal plates (for underclothing) or between a metal plate and free air (for outer layers). Each industry has its own specifications and methods for measuring thermal properties.