Plagiarism detection reports from companies such as Turnitin are the primary way that faculty identify cheating on written work. But my experience in working with hundreds of faculty has shown me that most misread these reports because they have not received proper instruction on how to interpret the results. In particular, faculty are not trained in how to distinguish cheating from ignorance of citation rules, and as a result students are often wrongly accused of cheating. Here I explain how to read plagiarism detection reports to both deter cheating and help students understand writing rules.