Abstract: A single cylinder deadbolt lock with a thumbturn includes a slidable pair of gear elements normally engaging the thumbturn with the cylinder whereby either one will operate the bolt. One such gear element is provided on a hub rotatable with the locking bar shaft, while the other gear element comprises part of the thumbturn mechanism. A rotatable sleeve coaxial with the locking bar shaft is also normally disposed in meshing engagement with the aforementioned hub but is restrained from axial movement. Axial movement together with rotation of the lock cylinder, e.g., for locking the mechanism, moves the hub and the sleeve out of meshing engagement, causing the hub and thumbturn to be held out of meshing engagement for disabling the thumbturn until the cylinder is again rotated.