A device for blind mounting of window panes can be designed optionally as a friction locking or positive-locking fixing variation.The device for fixing a movable window pane on a window regulator of a motor vehicle preferably has a substantially U-shaped base member which is open for inserting the edge area of the window pane. Side arms, with a first side arm, of the device are connected together through a base, as well as with at least one locking element mounted displaceable and/or swivelling. When the window pane is inserted in a gap of the base member, the locking element is supported on one side with the first side arm and on the other side with a side face of the window pane. The locking element is mounted resiliently against the insert direction of the window pane and/or across the plane of the window pane wherein a displacement and/or swivel movement carried out in the direction of the spring force reduces the gap of the base member, or with the window pane inserted, increases the pressure of the locking element on the window pane.