A cylinder lock having a body and a modified cam, the cylinder lock being adapted for moving an external element arranged to engage the modified cam, so that the external element slides axially on the cylinder lock body. In a preferred embodiment, the inventive cylinder lock is designed to utilize a helical cam which engages a movable sleeve, and this design is referred to as the HC cylinder lock. When operated by rotating the appropriate key within it, the movable sleeve can be moved in a linear fashion along the length of the HC cylinder lock thus converting rotational motion of the key to axial motion of the external element. This axial motion is used to position at least one locking bolt, of which the sleeve itself may be one, for the function of locking or unlocking a device. The streamlined design of the inventive HC cylinder lock enables efficient placement of a door lock within the hollow volume of a door.