Students build rectangles with pipe cleaners. Since the pipe cleaners are all the same length, the rectangles will all have the same perimeter. Students investigate the relationship between the base and height of each of these rectangles. Using multiple representations, students collect data in a table, graph the data, and build a symbolic rule relating base and height of rectangles of a given perimeter. A suggested extension of the lesson is to see how the areas of the rectangles vary. Guiding questions, summary questions, assessment tasks, and two activity sheets are included. (author/sw)