In Gliders, children construct simple paper airplanes that are remarkably elegant fliers. As in all Design It! projects, the children are acting here as engineers. Their task is to solve a practical problem and to pass on the knowledge of how they did it. We do not expect them to explain why things fly (lift, center of gravity, airfoils, etc.), as many well educated adults continue to struggle with those ideas. At the end of the process, we want the children to be able to name the few simple design principles (we call them "findings") that make the difference between a great flier and a dud. These principles might be of the type: the weight should be at the front, or rigid wings are better than floppy ones. If the children can recognize and state these principles in a way that other children can understand, then they will have learned an enormous amount about flight, about engineering, and about practical problem-solving and construction with these materials.