Every activity has its place in the classroom and is self-contained and self-correcting. The original didactic materials are specific in design, conforming to exact dimensions, and each activity is designed to focus on a single skill, concept, or exercise. All of the material is based on SI units of measurement (for instance, the Pink Tower is based on the 1 cm cube) which allows all the materials to work together and complement each other, as well as introduce the SI units through concrete example. For example, manipulative materials initially used to allow the child to analyze sense impressions are also designed to improve fine motor coordination needed for writing.
Other materials are often constructed by the teacher: felt storyboard characters, letter boxes (small containers of objects that all start with the same sound) for the language area, science materials (e.g. dinosaurs for tracing, etc.), scent or taste activities, and so on. The practical life area materials are almost always put together by the teacher. All activities must be neat, clean, attractive and preferably made of natural materials such as glass or wood, rather than plastic. Sponges, brooms ,and dustpans are provided and mishaps,including broken glassware, are not punished but rather treated as an opportunity for the children to demonstrate responsibility by cleaning up after themselves.)