Fixing A Boundary Line reviews boundary control and legal principles for professional land surveyors. The course addresses and enumerates many of the legal principles that control the boundary location of real property. Land surveyors play a key role in interpreting and implementing these often confusing principles. This course is associated with another RedVector course by the same author, Boundary Disputes Between Adjoining Owners. Together the two courses provide an excellent overview of some of the most common boundary problems that professionals encounter, with insights into practical solutions. With an emphasis on adverse possession, the course examines legal principles, including prescriptive easements, estoppel, acquiescence, practical location and unwritten agreements. It further explores conditional boundary lines and parol agreements, which are part of unwritten agreements. From these principles the course develops protocols for the professional to follow when encountering difficult situations. It also lists key references to use when a good boundary line solution is seemingly out of reach. The course emphasis is on the surveyor as a professional, as one who uses well-established principles of law to knowledgeably resolve boundary disputes and unexpected challenges.