A generic rectangle is used to simplify polynomial division. Generic rectangles are very helpful when it comes to arranging math problems so that there are fewer errors during calculations, according to mathrecreation.com.
A generic rectangle is essentially grid-and-lattice multiplication that breaks down the numbers into more manageable chunks and provides a way to keep track of the carries during calculations. Generic rectangles are also very similar to algebra tiles. An algebra tile is a manipulative that can be used for learning polynomial multiplication. For polynomials, generic rectangles provide a way to keep track of all those terms that come out of the distributive law.