We call this in English a "cheat sheet". If I am correct, you mean a little piece a paper that you hide in your sleeve and it has the answers to the exam written on it. If that it what you mean, then that is a cheat sheet. The dictionary definition is: 1.A document, especially a sheet of paper, containing information, such as test answers, used for cheating. Cheat sheet is two words, not a compound word.

A cheatsheet.