Abstract: A lock in which a replaceable control shaft adjusts a moveable shaft in the main cylinder to different predetermined levels. By adjusting the moveable shaft a new shear line is created between the key pin housed in the shaft and the spring loaded pin tumbler housed in a separate moveable shaft embodied in the lock housing. When a new shear line has been created a new predetermined key will become operable while the prior key, unless it is a master key, becomes inoperable.A special key when rotated causes a cylinder to rotate creating a cavity in the lock allowing access to the control shaft through the facing of the lock. The control shaft has a spring that compresses upon adjustment securing a nodule on the control shaft into one of several cavity slots. The control shaft has teeth that mesh into the adjustable moveable shaft. The teeth may or may not cause the moveable shaft to change position upon the rotation of the control shaft.