The Sex Orientation Scale (SOS) was Harry Benjamin's attempt to classify and understand various forms and subtypes of transvestism and transsexualism in biological males, published in 1966. It was a seven-point scale (with three types of transvestism, three types of transsexualism, and one category for typical males); it was analogous to the Kinsey Scale as it relates to sexual orientation, which also had seven categories. Much like Kinsey's understanding of sexual orientation, Benjamin understood the nature of gender identity and gender expression not as a discrete scale, but as a spectrum, a continuum with many variations. The Benjamin scale provides a rational and clinically useful way to understand different forms of transsexualism and to distinguish between how people commonly identif