Thanks. I do understand the mechanics, but the article seemed to imply that there are some flakes that people do use traditional cams to climb. I was more curious in how the line between safe and unsafe gets drawn than the theory behind why horizontal forces on flakes are dangerous. In other words: you pull on flake, and it moves - obviously, horizontal force is unsafe. But: how do you then decide a vertical force on the same flake is safe? Is it just feeling and experience, or are there actual rules people generally follow?