Greene defines a thumbscrew as a weakness. It can either be an insecurity, an uncontrollable emotion, or an insatiable appetite for a particular pleasure. Once you discover what a person’s weakness is and cater to it, you can use the person to your own advantage as “what people cannot control, you can control for them” (499).

You can find out a person’s weakness by listening and observing carefully. You may employ tactics such as revealing an allegedly heartfelt secret of your own and making it seem safe for the other person to open up or probing around a particular enthusiasm or emotion. As Greene writes, “what oozes out in the little things outside our conscious control is what you want to know” (485). He argues that the projection of one dominant trait, for example, shyness, often conceals the desire for the opposite.

The negative side of playing on people’s weaknesses is that you may elicit an action that is out of your control, as you can never predict the outcome. You should also not get carried away by the thrill of controlling your victims and lose sight of the specific thing you want from them.