Patent ID: 8794042

Claim:
In a key-operated lock, a plug assembly comprising: 1) a cylindrical key plug rotatable between a key insertion position and a control position, having a cylindrical periphery and a longitudinally-formed keyway, a plurality of radially-arranged tumbler bores that extend from the keyway to the periphery, and an axially arranged groove formed into the periphery of the plug and displaced circumferentially from the plurality of tumbler bores, the groove having, in cross-section, a radially-outermost carriage groove, a radially intermediate curved trough extending radially inwardly from the center of the carriage groove, and a control tool slot formed radially inwardly from the curved trough; 2) a carriage disposed and moveable axially within the carriage groove between a first and second position, having an outer surface proximate with the cylindrical periphery of the key plug, and having a plurality of radially-formed retainer bores that align circumferentially with the plurality of tumbler bores when the carriage is in the second position; and 3) a change tooling configured for manual insertion within the control tool slot to intersect at least a portion of the curved trough.