In instances where more than one invention is found in a single application, the applicant may incorporate the extra subject matter into one or more divisional applications which will receive the same filing date as the original application.

Chapter 800 outlines the requirements for a restriction including independence (when the subjects in question are not connected in design, operation or effect) distinctness (when there is a relationship between the subjects in question, but they are capable of separate manufacture and are patentable over one another), and many obscure details concerning the topics of restriction and double patenting.

The topic of restrictions is one of the most complicated areas of the MPEP. Fortunately, this subject is not tested too heavily on the bar exam. However, you may expect a tricky question relating to species, the differences between double patenting and 35 U.S.C. 102/103 rejections, and possibly a question related to the determination of distinctness or independence of claimed inventions.