Years ago, I was taking an algebra class over the summer, and had a teacher who liked to reminisce about his past with funny stories. He relates that he had been a math teacher in the Air Force, where it was his duty to force sleepy young recruits to stay awake for an hour of math at 8:00 in the morning in a large, warm, dimly-lit auditorium. One day, he came into the auditorium and saw his class even sleepier and less attentive than usual. He realized that something drastic would have to be done.
Now this classroom was very old, and the blackboards, which had been nailed on to the walls with old black iron nails, had become loose over the years. As a result, these black nails jutted almost invisibly from the blackboard and this teacher kept banging his hands on them while erasing the board. He decided to put them to good use.
With enough of a flourish to guarantee the class's attention, he went to the front of the room, near one edge of the board. Then, clearing his throat, he drew a coathook right near one of the protruding nails. He proceeded to hang his coat and hat on the hook that he had drawn in chalk (really on the nail, of course). Then he went on to give that day's lecture. He told us that the entire class had their eyes to the front of the room throughout the lecture. He didn't know if they'd heard a single word he'd said, but at least they looked attentive.
At the end of the class, the lecturer would usually leave by a small door near the blackboards, while the class would leave through the large doors at the back of the hall. When class was over, he took his coat and hat, erased the coathook, and left through the small door--and was followed by the entire class, lining up to go past the blackboard to see how he'd done it.