[neaden]

They're kind of vague on what the solution is since they don't want to give it away to the audience so they just kind of say a hint. The attempted fooler will generally understand what they are getting at and say if they are correct or not and there are some judges listening who know how it was done as well.

[seanc]

Unless the contestant is an ass about it, in which case they blow the secret wide open. That part's fun too.