Mul-T-Lock is a high security lock cylinder distinguished by the use of a telescoping “pin-in-pin”—tumbler design. Picking the Mul-T-Lock cylinder with a traditional picking tool is highly complicated because it can get stuck between the inner and outer pins. The H&M Mul-T-Lock picking tool was designed to overcome this problem and facilitate the picking of the “pin-in-pin” cylinder. The purpose of this research is to determine whether H&M Mul-T-Lock picking tool leaves class characteristic mark and whether it can be distinguished from traditional picking tools marks and from regular key marks. It also describes and determines the class characteristic mark left on telescopic pins, its origin, recurrence, and its benefit to the toolmarks examiner. When receiving a Mul-T-Lock from a crime scene, a toolmarks examiner can quickly determine whether or not it was picked by an H&M Mul-T-Lock picking tool by noticing the class characteristic mark which this typical tool leaves.