The invention relates to a fastening device having at least one positionable holding device, comprising a base plate having an extensively flat rear surface and a front surface, opposite the rear surface, wherein a first guide channel is formed on the front surface. The guide channel is delimited by side walls, wherein engagement areas are formed at least in sections on at least one of the side walls. According to the invention, a slide element is arranged in the guide channel, which can be displaced along the guide channel, wherein the slide element has a carrying element, wherein two spring elements are formed on the slide element, which can engage with the engagement surfaces of the guide channel in a blocking position, and wherein there is a movable locking element on the slide element, which fastens the spring elements at least in the blocking position.