Various embodiments include a device securing an actuating drive on a duct outer face of an HVAC duct against rotation. The actuating drive includes an actuator for driving an actuation connection about an actuation axis. The actuation connection interacts with a flap arranged in the ventilation duct to set a gaseous volumetric flow. The actuating drive includes a housing with a ledge formed on a bottom side of the housing and surrounding the actuation connection coaxially relative to the actuation axis. The housing bottom side lies opposite the duct outer face. The device may include: a fastening part for fastening to the outer face; and a fork-shaped receptacle formed at an end. The receptacle geometrically matches a radial outer face of the housing ledge such that after lateral sliding onto the outer face of the ledge, the receptacle fixes said ledge and thus the actuating drive against rotation.