Shading system with guide rails and gain profile

A shading system has a curtain (12) which is guided over its extension length in two lateral guide rails (14), between the guide rails (14) at least one reinforcing profile (22) is provided. To a more constant fabric tension in the transverse direction to achieve independently, for example, the influence of the cloth holder or assembly inaccuracies, it is proposed that the reinforcement profile (22) variable in length is formed.