Abstract: A quick-fastening element (10) is used to anchor loads to profile rails (12a, 12b). It has a mounting part (18), a cage (20), and a movable closing nut (22). To improve the screwing-in motion and to enable more universal use of the quick-fastening element, it is proposed that a first spring element (24) is provided between the closing nut (22) and the mounting part (18), and a second spring element (26) is provided between the end of the cage (20) and the closing nut (22), and the closing nut (22) is in a position of equilibrium.

Abstract: A method for constructing a resilient floor on a solid base utilizes plate-shaped elements. Hollow, height-adjustable elements are fastened on the base and are filled with an elastically hardening material, which is adhesive in the flowable state. Prior to hardening, base plates are placed on the filled elements and are aligned. When lifted, the base plates move the elements located below them because of the adhesion of the filler material to the base plates. After hardening, at least one further floor layer is placed on the base plates. This method can be executed rapidly.

Abstract: The projector has an essentially afocal projection system, in particular for the reproduction of three-dimensional images. This system has a system of convex lenses (1) on the side of the object and a Fresnel lens (2) on the side of the image. The lenses are larger than the transverse dimension of the object to be reproduced. By providing a double reflection (3, 4), this projection system is able to generate, in addition to the reproduction of two-dimensional images, a three-dimensional image of a real, three-dimensional object, "positioned in space" and whose sides are correctly aligned for the benefit of an observer. Preferably, a plane mirror (3) is used for this purpose as well as a beam splitter (4) that is inclined by about 45.degree. with respect to the main axis (5) of the system of convex lenses (1).