Problem-solving research has consistently found that students have great difficulty when asked to apply concepts and principles discussed in texts and lectures. It is often unnoticed knowledge extensions or transformations that allow faculty experts to solve such problems. Because faculty members normally use these extensions automatically, they do not emphasize them in their teaching. Therefore, knowledge transformations often remain completely hidden to students. This paper presents a first attempt at a field guide to help faculty members identify and teach about hidden knowledge transformations. Examples from introductory psychology and physics teaching are included, along with some pedagogical techniques that have been found to be helpful in dealing with these in both disciplines.