Telescoping pin

A telescoping pin is a modification of the traditional pin-tumbler design that allows for "pins within pins". In a telescoping design, there are outer and inner pins, all of which must be properly aligned at the shear line to allow the plug to rotate.

Though the design of the telescoping pin goes as far back as 1897, companies like Mul-T-Lock and KESO are credited with popularizing and innovating the design in modern pin-tumbler locks.