Students are introduced to vocabulary and notation related to rigid motions (e.g., transformation, image, and map). Students are introduced to transformations of the plane and learn that a rigid motion is a transformation that is distance-preserving. Students use transparencies to imitate a rigid motion that moves or maps one figure to another figure in the plane. The goal of this module is to arrive at a clear understanding of the concept of congruence (i.e., What does it mean for two geometric figures to have the same size and shape?).