As the result of a qualitative investigation into spatial ability, a teaching technique called mentored sketching was found to be effective for teaching visualization skills to freshman engineering students. This contribution describes the technique, how it evolved, and comments made by students as to its effectiveness. While mentored sketching emerged as a novel approach for the advancement of student sketching and spatial ability skills, it appears unhindered by class size and provides few constraints as a teaching methodology. (Contains 2 figures.)