What label other than white might have been utilized to divide laborers? What are the possibilities and limitations of the label you suggest?

Laborers were not only divided by race; they were also divided by gender and into skilled versus unskilled workers. The Knights of Labor, founded in 1869, was the nation's first major labor union. The Knights of Labor accepted all workers, including those who were skilled and those who were not. After the Knights of Labor declined, the American Federation of Labor (AFL), founded in 1886, only accepted skilled workers and white, mostly male workers. These workers were organized into craft unions.
Therefore, the label "skilled" workers was used to divide laborers. The possibilities of this labor union (the AFL) included its ability to advocate for better wages and working conditions for skilled workers, and it also was able to advocate for shorter working hours. The union had leverage because the workers it represented were needed by employers.
However, as the source below points out, the AFL had a number of limitations because it did not represent a large swath of the work force. As the source below notes, by the 1920s, many of the new industries, such as automobiles and chemicals, involved mass production and the use of unskilled labor. Therefore, the union came to represent fewer people, and membership declined. Most women were unskilled laborers, so they were also mostly left out of the AFL. Dividing workers into skilled and unskilled labor has the advantage of representing people who are valued by employers, but this division leaves out a large percentage of workers.