SMOM-SLlP SYSTEM FOR SHOWER TRAYS OR BATHTUBS in the name of: FURlA MARMI E GRANiTl S.f.l of Cason di Rivoli Veronese (Verona - Italy) DESCRIPTION This patent proposes a non-slip system which is particularly suitable for use in shower trays or bathtubs. It consists of a system that presents a shower tray or similar surface made of the close union of multiple elements, one at least of which is made of a non-slip material, closely joined together in order to form a single body. As is well known the surfaces of shower trays or bathtubs internal support bases are usually made of material such as ceramic, porcelainized gres or other. These materials, in combination with water, make these bases slippery and easily cause the persons inside the shower stall or bathtub to slip. Means for overcoming this important and dangerous risk of slipping and consequent injury consisted of, first of all, modifying the surfaces of the shower trays themselves, giving them special undulations, reliefs or projections designed to favor greater adherence and safer contact between the base itself and the feet of the person in the shower stall or bathtub. These adjustments in the form of the support surfaces have not brought a good solution to the slipping problem and, for this purpose, further means were introduced, using special mats and/or strips of rubber or other material or more or less thick wooden duckboards, which components were positioned on top of the ceramic, PVC or fiberglass support surface and held in place on them. These solutions have only partially solved the slipping problem: rubber strips or mats, in fact, are anchored to the support surface by suckers or special glues which, subject to the presence of water, do not guarantee a strong and enduring connection. Consequently the presence of said mats or strips or other material not infrequently causes unfortunate situations that, rather than prevent, favour people to slip inside the shower stall or the bathtub. As far as use of wooden duckboards is concerned while it is true that they ensure greater safety than rubber mats they also more easily deteriorate. In addition the esthetic result is assuredly not very satisfactory in both cases, whether speaking of mats or rubber strips or wooden duckboards. The purpose of the invention is to create a shower tray or bathtub comprising of the combination of one or more elements closely joined together, one at least of which is made of a non-slip material, such as marble, agglomerate, stone, ceramic or other similar materials with special non-slip treatments such as glass materials, there being in the shower tray or the support base inside the tub one or more seats designed to house said non-slip elements and permit their intimate union, forming a single body. Thanks to this object of patent we achieve, first of all, the advantage of preventing, in an optimum manner, slipping by the persons present in the shower stall or bathtub thanks to the presence of a more or less rough surface that ensures friction between the surface itself and the feet of the person positioned on top of the element. In addition the non-slip stone material element is combined with a second element having a special seat that favours joining and makes it practically impossible to move the non-slip element itself. Another advantage achieved with the system according to the present invention concerns the aesthetic result which is pleasing because it employs an element made of stone or glass or ceramic or other similar material coming in various colors and tones depending on the natural or artificial materials available on the market and on the purchaser's requirements. The purposes and advantages mentioned above are all achieved, according to the invention, by a non-slip system for shower trays or bathtubs characterized by the fact of comprising a shower tray or similar surface made of the close union of multiple elements one at least of which is made of a non-slip material, closely joined together in order to form a single body. Further characteristics and details of the invention can be better understood from the following description which is given as a non-limiting example and which refers to the attached drawings where: fig. 1 shows a schematic and axonometric view of the non-slip system made on a shower tray; fig. 2 gives a lateral section view of the system in figure 1 ; fig. 3 is a view from above of the non-slip system object of this patent and used for a shower tray. With reference to the attached figures 1 indicates the overall non-slip system according to the invention using realization methods that permit it to be used on the inner surfaces of tubs, shower trays, sanitary fixtures in general or the like. Non-slip system 1 consists of joining multiple elements 2, 3 made of non- slip stone material in order to create shower trays or bathtubs consisting of a single body. More in detail upper element 2 is made of a stone material such as marble, granite or other cement or ceramic or agglomerate material, material that has at least one surface, specifically at least the upper surface that is walked on, treated with special satin-finishing or honing processes that give it non-slip characteristics. In addition said upper element 2 may in case be subject to anti-stain treatments, preventing element 2 from being subject to stains or other abnormalities caused by damp deposits. Lower element 3 of the shower tray or bathtubs has a seat 4 designed to house non-slip element 2 to which it will automatically connect because seat 4 itself has a homologous shape compared to element 2 which can be seen in figure 2. We can also see that the combination of upper element 2 with lower element 3 presents specially bevelled and rounded lateral corners 5,6 for greater comfort for the persons in the shower stall or bathtub, preventing cuts or bruises. This patent also presents the creation of non-slip element 2 and consequently its related housing seat 4 in many shapes; non-slip element 2 can in fact not only be square in shape but also circular or polygonal depending on the position where the shower tray must be placed or depending on the shape of the bathtub. It also presents the combination of multiple elements 2 on one or more seats 4, to make the non-slip system extremely pleasing even from the esthetic point of view. The particular combination of non-slip element 2 with its housing seat 4 can be made not only by a natural joint between the two parts owing to their reciprocally homologous shapes but by special gluing or fastening systems. In addition it is also possible to create joining seat 4 with a raised part designed to be inserted into an homologous seat present on non-slip element 2. It can also presents the fastening of the upper element 2 to the lower element 3 without seat 4, clamping upper element 2 to lower element 3 using suitable fastening means such as glues or other bonding elements. In addition it is necessary to specify that the present non-slip system does not complicate creation of the plumbing system for the shower or tub because the outflow of water always takes place through the drain that is generally positioned in a corner location. A technician in the sector may provide for several modifications or variations, achieving solutions that are to be held as included within the invention protection scope and further defined in its specific characteristics by the following claims.