Abstract: An automatic opener for a sectional door includes a drive unit mounted adjacent to a door drive shaft and having a reversible motor, a gear linkage for translating rotation of the motor drive shaft into rotation of the sectional door drive shaft, and a clutch which permits the gear linkage to be manually temporarily disengaged from the motor drive shaft. The drive unit is supported within a housing that is connected to an adjustable wall bracket mounting base which itself is fixed to a wall adjacent to the sectional door. A spring-biased lever attached near a lower end of the sectional door pivots in response to slack in a door cable to automatically lock the door when it is completely shut. The locking mechanism automatically unlocks the door either when the drive unit is actuated to open the sectional door or when the clutch is utilized to disengage the gear linkage from the motor drive shaft.