A pin tumbler lock of a first embodiment includes a shell containing top pins; and a plug, rotatable within the shell, containing standard bottom pins, and a shorter bottom pin, set back from the face of the plug. A tubular key has bitings corresponding to the standard bottom pins, and a projection corresponding to the short bottom pin. When the key is inserted, the bitings and the projection press all the bottom pins to the shear line. In a second embodiment, a lock includes a shell containing top pins and a depression; and a plug, rotatable within the shell, containing bottom pins. The depression is configured and dimensioned to receive one of the bottom pins. The depression may be opposite one of the bottom pins, and there may be one more bottom pin than top pins. When the key is inserted, the bottom pins are moved to the shear line.