Slave (work), or Work slave (slave designation) a category of slaves consisting of field slaves, stable slaves, etc. These females are considered, like kettle-and-mat girls , to be low slaves.
Female work slaves, field slaves, stable slaves, and such, like kettle-and-mat girls, are usually considered the lowest of slaves. At any rate, they commonly bring the lowest prices in the markets.
Book 25, Magicians of Gor: Page 305