Machinist's Mate 2nd Class Brenton Robbins, center, uses a frisker on Chief Machinist's Mate Jason Cathey, right, during a radioactive contamination drill in the medical decontamination room aboard the aircraft carrier USS Harry S. Truman. A frisker indicates radioactive exposure on skin or clothing with a series of high frequency clicks, simulated here with pen clicks by trainer Machinist's Mate 2nd Class David Lechear.