In her 1990 work, Race, Class, and Gender: An Anthology, Collins suggests that the interaction of the three variables help to create a "matrix of domination."  This idea brings out how all three forces converge to consolidate power of one particular group over another:

Because of their [race, class, and gender] simultaneity in people's lives we advocate using the approach of a "matrix of domination" to analyze race, class, and gender as different but interrelated axes of social structure. A matrix of domination posits multiple, interlocking levels of domination that stem from the societal configuration of race, class,and gender relations. This structural pattern affects individual consciousness, group interaction, and group access to institutional power and privileges (Collins 1990).

The idea of a "matrix of domination" helps to explore how the variables of race, class, and gender interact with one another.  They are constructions of power that enable particular people to be relegated to "the outside" while others enjoy privileged status of being "on the inside."  These variables help to feed the inequality in American society because of their ability to keep others out of power and others within it.  Power becomes a tool through which variables such as race, class, and gender are able to be wielded in order to ensure control is present. They do not operate outside of one another.  That is to say that discourse is not necessarily served with one being seen as more dominant than another.  They work in tandem with one another to fully prevent the enfranchisement of individuals.  In this construction of a "matrix of domination," there is a greater interplay between these variables that help to contribute to inequality in American society.