an actuating device actuates a shading system with a string element . an unintended detachment of a first partial structure from a second partial structure in the intended use is avoided as much as possible and a detachment of the first partial structure from the second partial structure is possible with low forces for avoiding injuries . the actuating device includes a first coupling element that in the released position does not mesh with a second coupling element , and in the locking position , with an interaction of the first coupling element with the second coupling element , a detachment of the first partial structure from the second partial structure is prevented because of a positive - locking connection between the first coupling element and the second coupling element .