This Instructional Activity is a part of the Lesson 12, Unit 1, Grade 6. This activity encourages students to apply strategies for finding the area of polygons to finding the surface area of rectangular prisms. Students use 12 cubes to build a prism, think about its surface area, and use isometric dot paper to draw their prism. As students build their prisms, notice those with different designs and those with the same design but different approaches to finding surface area (e.g. by counting individual square, by multiplying the edge lengths of rectangular faces, etc.).