The Equalizer is a visual guide to help teacheres think about tiering tasks and products (see Tiering). By matching task difficulty with learner readiness, a teacher can provide appropriate challenge for a given learner at a given time. For example, if students in a math class are working with measurement, their teacher might ask them to measure the surface area of a desk. If the teacher asks students having difficulty with measurement to measure the surface area of the classroom floor, that task, on the Equalizer, would be relatively "foundational"--that is, similar to the familiar, in-class task. If, one the other hand, the teacher finds that some students have a solid grip of the in-class task, the teacher might assign a task such as measuring the surface area of a tree. That task is much more "transformational," or unfamiliar. In this way, both groups of students can continue to advance their ability to measure surface area, but at appropriately different degrees of difficulty. (Tomlinson & Strickland, p. 351).
C. Tomlinson & C. Strickland (2005) Differentiation in Practice: A Resource Guide for Differentiating Curriculum Grades 9-12. ASCD.