Abstract: A key-activated removeable cylinder lock is disclosed. The lock has a lock barrel including a plurality of combinating tumblers disposed therein for movement between a first resting position and a second activated position. The barrel further includes a control tumbler having a first end and a second opposite end. The control tumbler is slidably disposed between a first resting position and a second activated position. In the resting position, the first end is extended relative to the barrel. In the activated position, the first end is retracted relative to the barrel. A housing rotatably removably receives the barrel therein. The housing further has an internal longitudinal slot formed therein extending from a forward end thereof. An annular clearance space is located rearwardly of the slot and is in communicaiton therewith for accommodating extension of the first end of the control tumbler in the resting position, whereby rotational movement of the barrel in the housing is permitted.