An arrangement for at least partially covering a window

An arrangement for at least partially covering a window, wherein the arrangement comprises a covering adapted for being arranged in different intermediate extension states between a retracted state and an extended state for covering the window to different extents, and wherein the arrangement comprises an elongated support element, wherein the covering is supported by the elongated support element and movably arranged in a longitudinal direction of the elongated support element between the different extension states in the extension direction, wherein the elongated support element is at least substantially rigid, the arrangement further comprising at least one rotary knob for controlling a position of the covering in relation to the rigid elongated support element, wherein the rotary knob is arranged accessible for manual operation, wherein the arrangement further comprises a stop member that is adapted to engage with the rigid elongated support element and a transmission adapted for transmitting a rotary movement of the rotary knob to a movement of the stop member towards and/or away from the rigid elongated support element so that the stop member may be moved between a position in contact with the rigid elongated support element in an advanced position for holding the covering stationary relative to the rigid elongated support element and at a distance from the rigid elongated support element in a retracted position for allowing movement of the covering relative to the rigid elongated support element.