Knowledge of the history of interactive prints, which present a moveable paper object within the printed work that can be manipulated by the reader, is crucial to understanding their function and use. Examples of interactive prints of early modern printed books such as Euclid’s Elements, Blagrave’s The Mathematical Jewel, or Vesalius’ Humani corporis show how moveable parts in books were commonly used at that time. They were a helpful tool to display astronomical content in books or cheaper versions of astronomical instruments made of paper. To assist in the investigation and understanding of the use and application of volvelles—moveable paper instruments in the form of wheels—a basic outline of astronomical instruments and of the concept of stereographic projection is given in this chapter.