This paper explores a new tool for instructional designers. By calculating and graphing the Student Momentum Indicator (M) for 196 university-level online courses and by employing the constant comparative method within the grounded theory framework, eight distinct graph shapes emerged as meaningful categories of dropout behavior. Several of the graph shapes identified Course Walls, that is, areas of the course's lesson sequence wherein the student's momentum to finish the course is significantly slowed or halted. We posit that instructional designers can apply the evaluation of Course Walls to course revisions to reduce dropout rates.