I can recall about 25-30 years ago when my very computer illiterate boss was handed a laptop by one of the geeks in the IT dept. He would not take it back and told my boss to call the IT manager as he (the geek) was told to leave it.
One of my coworkers, did a little training to help my boss and told him that to erase the screen that he should hold the laptop over his head and shake it.
He had prepared things very well as he demonstrated it and unbeknownst to my boss, he pressed a key or two to clear the screen as he moved the machine over his head to demo the method.
Our boss could not master erasing the screen that day but someone did let him know later that he had been had!