Abstract: A fixing device for an actuator to control the opening and closing of a leaf of a door or a gate has a hinged support assembly that includes a part fixed to the pillar and freely hinged at a first location to one end of the actuator, an elongated body hinged at a first end to the part fixed to the pillar and offset from the hinge of the actuator, and hingedly coupled at its other end to the distal end of the actuator, and an arm articulated at a first end to the leaf and hingedly coupled at its other end to the elongated body opposite the part fixed to the pillar. The actuator, the elongated body and the arm are substantially aligned with each other and angularly aligned with the leaf to form a triangulation in the closed position for providing angular locking of the leaf in the closed position. A hinged part of the elongated body taking the arm for coupling to the leaf is equipped with an arrangement for providing temporary locking of the leaf in an open position.