You might say that the woman next door has a green thumb if her garden continues to grow long after your plants have died.

VOA: special.2010.05.23

Middle finger exactly and your thumb.

中指和姆指。

哈佛公开课 - 幸福课课程节选

So-- if you don't feel comfortable doing it, don't do it-- what I'd like to do now is as following: Take your thumb and your middle finger and create as much as possible a 90 degree angle.

感觉不舒服的，就不要做，希望按下面的指示做：,让你的姆指和中指,尽可能形成一个直角。

哈佛公开课 - 幸福课课程节选

Are there other indicators or tricks or rules of thumb that just off the top of your head come to you as useful mechanisms for doings this as well?

当然还有没有其他的,一些暗示或者说技巧,或者规则之类有用的办法呢？

哈佛公开课 - 计算机科学课程节选