There is also the optional rule of "Critical Successes" and "Critical Failures". If using a d10, rolling a 10 is a Critical Success, and allows a second roll. The result of the second roll is added to the first to calculate the result. Further 10's may be rerolled. A roll of 1 is an critical failure and you subtract 1d10 from your total. When using 3d6; a roll of all sixes, (an 18), is a Critical Success, and two additional dice can be rolled and added to the result. A roll of three ones, (a 3), is a Critical Failure, (even if all you only needed to roll was a 3 to succeed the check), and subtract 2d6 from the total. A Critical Failure may represent something more disastrous happening to the character as the Referee sees fit. A Critical Failure on a Lockpicking task, for example, could trigger a silent alarm the character wasn't aware of.