Abstract: The invention relates to a fastening means provided for engaging with factional or positively locking means in a friction or positively locking fashion comprising a protuberance realized as an extrusion, wherein the protuberance projects from a plate expanding along a main plane and having a prime surface facing away from the protuberance and comprises an inner side, wherein the inner side forms a circle having an inside diameter Di in a plane being parallel to the main plane, wherein a first plane being parallel to the main plane includes a circle with the first inside diameter Di? and a second plane being parallel to the main plane includes a circle with the second inside diameter Di?, and wherein the first plane is closer to the prime surface than the second plane, and wherein the first inside diameter Di? is greater than the second inside diameter Di?.