What is the strangest thing your father ever taught you?

This is a kind of research. I don’t expect many answers but hopefully you guys can help me out.

Better put: what is the most frightening or disconcerting thing he ever taught you?

I mean ‘taught’ in the pedagogic sense. I mean something he explained directly and verbally to you. I do not mean the lesson you learned about fathers being the scum of the earth when he walked out while you were still in grade school although if that’s the case feel free to share your story because it would be interesting as well and I don’t want to discriminate etc.

The most important part of the question for me: how did he explain this to you? What kind of language, gestures were involved? Where did it occur? The details interest me the most.

Thanks in advance.