throughout all the figures , same or corresponding elements may generally be indicated by same reference numerals . these depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way . it should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols , phantom lines , diagrammatic representations and fragmentary views . in certain instances , details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted . turning now to the drawing , and in particular to fig3 , 3 a and 3 b , there is shown with the reference symbol 11 a mounting support for mounting rigid photovoltaic modules 13 on an uneven roof panel . the roof panel is composed of a plurality of shingles 15 which are nailed in overlapping relationship onto a wooden substructure 17 , typically with roofing nails ( not shown ). the shingles 15 may be made of sand - coated roofing felt , wood , or other suitable materials . due to the overlap , a step 19 is formed in the overlap region , which for an installation of the shingles 15 with an offset is maximally twice the shingle thickness . the photovoltaic modules 13 are to be installed on this type of roof panel . to this end , the mounting support 11 is composed of a strip 21 having attachment means 23 arranged in regular intervals , the so - called modular dimension . each attachment means 23 has on its top side two supporting surfaces 25 , which each support an edge of adjacent pv modules 13 . the two supporting surfaces 25 are separated from each other by a separation wall 27 which prevents adjacent modules 13 from striking each other and also operates as a stop during installation of the pv modules 13 . the attachment means 23 has on its bottom side a padding 29 made of an elastic material , operating as a seal when compressed . in the illustrated exemplary embodiment , the padding 29 extends across the entire underside of the attachment means 23 . it would also be sufficient to use a round or rectangular padding 29 with a diameter or edge length between 5 mm and 20 mm , as described below when discussing its functionality . each of two attachment means 23 are connected with one another by way of the longitudinal rail or strip 21 . to illustrate the two variants shown in fig3 a and 3 b , fig3 shows on the right side a single - screw variant and on the left side the three - screw variant . it should be noted that in reality the support is always equipped with only a single type of attachment means 23 . in the illustrated embodiment , the strip 21 and the attachment means 23 are manufactured as a single part , for example , by an injection molding process . the variant illustrated on the light side in fig3 a includes a bore 31 located in the central region of the attachment means 23 . the bore 31 extends perpendicular to the supporting surfaces 25 and is preferably implemented so as to terminate before the padding 29 or to slightly penetrate into the padding . a screw 33 is inserted through the bore 31 , and the thread of the screw 33 is screwed into the wooden structure 17 located underneath the shingles 15 . a clamping part 35 , which has at its bottom side a rubber part 37 to prevent sliding and scratching of the pv modules 13 , is provided as an accessory to the attachment means 23 . a protective foil ( not shown ) similar to the rubber part 37 can be applied on the supporting surfaces 25 of the attachment means 23 before installation of the pv module 13 . the diameter of the bore 31 may be larger than the outside diameter of the screw 33 , allowing the screw 33 to move freely inside the bore 31 . to prepare the mounting support 11 for installation ahead of time , the diameter of the bore 31 should be slightly smaller than the diameter of the exterior thread of the screw 33 . in this case , the clamping part 35 can already be positioned during manufacture of the support 11 and can be rolled up together with the mounting support 11 , held in place by the screw 33 . as seen clearly in fig3 a , the padding 29 is compressed after the clamping part is pressed against the pv module 13 and protects the region where the screw 33 penetrates the shingles 15 from incursion of moisture . the complementing fig3 b shows the three - screw variant , where the central bore 31 is replaced with a blind hole 38 , with the bottom of the blind hole 38 terminating a safe distance from the underside of the attachment means 23 . if the material from which the attachment means 23 is made has a sufficiently high firmness , then the inside of the blind hole 38 can be directly provided with an interior thread . the clamping forces are then directly introduced into the attachment means 23 . conversely , if the attachment means 23 is made of a softer plastic , then a metal sleeve should be anchored therein during manufacture of the attachment means 23 , whereby the clamping forces are then transmitted indirectly via the sleeve to the attachment part 23 . fig4 shows a top view onto the basic component of the mounting support 11 in the smallest unit of the strip 21 , which forms only a single longitudinal rail , having only one respective attachment means at each of its ends . the pv module 13 is installed on the roof panel by installing two of these basic components next to each other . fig5 shows the next larger structure , wherein the strip 21 has the length of several meters and includes several attachment means 23 . the attachment means 23 are spaced from one another with an identical distance a , thereby forming a modular dimension a . the strip 21 then includes a plurality of longitudinal rails 21 a to 21 e which each connect two corresponding adjacent attachment means 23 with one another . fig6 shows two adjacent basic components according to fig4 , wherein two strips 21 and 21 ′ are arranged next to each other and the opposing attachment means 23 and 23 ′ are connected in pairs by way of a transverse rail 39 . a still more complex structure of the mounting support 11 which is prefabricated as a single piece is shown in fig7 . the row structure of fig5 is combined with the rectangular structure of fig6 , forming a structure similar to a rope ladder . in other words : all attachment means 23 and 23 ′ located along the strips 21 and 21 ′ at the same position in the strip 21 , 21 ′ are connected in pairs via a respective transverse rail 39 . the largest possible type of mounting support 11 is obtained when several of the ladder - shaped arrangements of strips 21 , 21 ′ and attachment means 23 , 23 ′ shown in fig7 are combined next to one another into a grid 41 , as illustrated in fig8 . this figure also shows the connection scheme of the involved 16 pv modules . the positive terminals of the pv modules are indicated by a plus - sign and the negative terminals with a minus - sign . the cable connections are indicated by continuous thick lines , which need only be connected from one module 13 to the next module 13 ; a longer connection is sometimes required which can be implemented via external cables with clamps formed on the rails or with electric cables integrated in the rails . fig4 shows another electric cable 43 which is integrated inside the longitudinal rails 21 and the transverse rail 39 . alternatively , attachment with an adhesive to the bottom or top side of the rail 31 : 39 may be selected . the ends of the electric cable could either be provided with a first component of a plug connection , or with a contact pad 45 which provides electrical contact to the pv module by way of pressure . while the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail , it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention . the embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated .