The topic of this final paper is the application of the cross-section core, but also the concept and the process of construction of the core and its calculation are explained. In addition to the core, complex load of rods is explained, i.e., eccentric axial load, because analytical and graphical structure of the core derives from this. In addition to the process of obtaining the core, it is necessary to understand what the core is used for and in this final paper some situations (loads) are shown in which the importance of the cross-section core is emphasized. This is shown on the example of a unilaterally fixed straight rod loaded with biaxial bending and eccentric loading. Examples of how the core of the cross-section is constructed are also solved, and in addition, in the first example the eccentricity of the force is determined, so that stress does not occur at an arbitrary point of the cross-section, while the second example shows the girder for which it is necessary to determine the load and the normal stress diagram.