What is topping from the bottom?

[leah06]

When I don't know a phrase I look it up on Wikipedia or elsewhere and usually I get a good working definition, but I don't understand this at all. How does this differ from negotiating? Does it mean being manipulative? So many of these interactions seem to involve saying one thing and meaning another, or having different layers of meaning, or doing one thing but signifying something else, so I don't know what this is in particular or why it's so bad to do.