Chapter 4 analyzes the doctrine of patentable subject matter. Delving into American, European, and Japanese patent jurisprudence, it first describes how these legal systems handle software-related inventions in general. Next, it applies that jurisprudence to 3D printable files to demonstrate why only one of the three 3D printing file formats is likely to constitute patentable subject matter. More intriguingly, it turns out that this file format is of least interest to would-be patent holders. In other words, a patent protection gap exists. Chapter 4 also analyzes jurisdictions’ differential treatment of patent claims directed to electronic signals. The Japanese and European patent systems consider these claims to be patentable subject matter, whereas the U.S. system does not. The upshot is that patent protection for software and 3D printable files is weaker in the United States because most 3D printable files are sold as internet signal transmissions. I argue that the United States should provide protection for signal claims.