Abstract: An opener for a sliding panel closure of a wall opening has a toothed belt horizontally disposed between a toothed sprocket and an arcuate grooved shoe located within a threshold plate extending across the opening adjacent a channel strip within which the panel slides. A bracket attaches the panel to the belt which moves the panel between closed and open positions by a shaft coupled through an electrical clutch between the sprocket and a motor. A solenoid driven armature raises and lowers a pin relative to the sprocket teeth to lock panel movement. A handle and latch provides override to unlock the panel for manual operation. The motor, clutch, solenoid and all other electrical components are separately housed marginally of the opening, at a location above the threshold to protect them from water.