In a lock drive train, the combination includes a pivoted lock bolt to be carried by a door, a casing, a rotary cylinder operatively rotatable during door opening or closing, a rack driven endwise in response to cylinder rotation, a gear rotatable by the driven rack, a pivoted lock dog driven by the gear, a bolt release lever, pivotable by the gear, between angular positions in which it is retained by the lock dog, the angular positions corresponding to extended and retracted positions of the bolt.