Re-keyable lock and method

A re-keyable lock and method. The lock has locked and unlocked positions and includes a housing and a cylinder rotatably supported in the housing. The lock includes a plurality of wafer tumblers resiliently supported in corresponding channels formed in the cylinder. Each wafer tumbler includes a rider element selectively engaged with a base element in first and second engagement positions, wherein the first engagement position corresponds to a first key and the second engagement position corresponds to a second key. The lock also includes a re-keying mechanism such as a re-keying tool which is inserted in a re-keying slot when the lock is in the unlocked position to disengage the rider element from the corresponding base element in the first engagement position and to re-engage the rider element to the base element in the second engagement position.