Rekeyable lock cylinder

A rekeyable lock cylinder which inserted a first matched key for unlock in a first direction and utilized a rekeying tool for rekeying, comprising:

• a plurality of first rack components;
• a plurality of second rack components selectively engaged with the first rack components and movable via contacting against the first matched key;
• and
• a guide bar having a first surface engaged with the first rack components, a second surface corresponded to the first surface, a first side in connection with the first surface and the second surface, a second side in connection with the first surface and the second surface, and a tool-receiving portion recessed into the first side, wherein the second surface is formed in a smooth shape, the tool-receiving portion is parallel to the first direction, and the first rack components are actuated by mentioned guide bar via acting force applied by the rekeying tool accommodated in the tool-receiving portion therefore enabling the first rack components to move in a transverse direction relative to the first direction and disengaging the first rack components from the second rack components.