This chapter features small wooden or cardboard boxes that hang about 5 feet from the ceiling on a short length of string. A second string comes out of the bottom of the boxes. The purpose of the boxes is not immediately clear because the inner workings are hidden from view. A slight downward pull on the lower string will cause the boxes to climb upward on the support strings. If the contents of the boxes are kept hidden, this will challenge students to make simple measurements and offer testable solutions on the action of each box. This activity is appropriate for upper elementary school students and above.