A threat roll is made when an attack roll hits and the natural (unmodified) roll is within the threat range of the weapon being used. This threat roll is made the same way as the original attack roll (with the same modifiers), except the threat roll does not automatically hit if a natural 20 is rolled, nor does it automatically miss if a natural 1 is rolled. (Plus, a threat roll cannot trigger another threat roll.) If the threat roll hits, then the original attack becomes a critical hit.