A laborer or labourer—see variation in English spelling—is a person who does one of the construction trades, traditionally considered unskilled manual labor, as opposed to skilled labor. In the division of labor, laborers have all blasting, hand tools, power tools, air tools, and small heavy equipment, and act as assistants to other trades, e.g., operators or cement masons. The 1st century BC engineer Vitruvius writes in detail about laborer practices at that time.