As a student at Utah State, I had a class called "Fundamentals of Calculus". It was a class designed to help students understand the rigors of mathematical proofs and then move on to two classes in which students prove all the basic tenets of calculus.
To study, I often used a study room in the Sci-Tech Library (which I understand has a different name now); the room had to be scheduled as it was busy especially as midterms or finals approached. I found the room handy because I could use the white board to outline proofs and then rewrite it on paper without wasting 10 sheets of paper before a final draft. This meant I often filled every little corner of the board cramming stuff between lines and vertically. So one day I was just finishing up when a group of students wanted to get started early. I packed my stuff and, forgetting to wipe the white board, left the room as several of the students billowed in. One girl, who upon seeing the white board, let out a shriek and then screamed "What is that on the board?" I grinned ear-to-ear as I walked down the hall. I am not sure I would understand even half of that anymore.