When calculating the supporting structures of ships, submarines, airplanes and vehicles, their armor is often treated as a support of variable section, loaded with given external forces. If that section changes abruptly, then additional internal forces appear, which elementary calculus does not show and which are not insignificant. The study of the action of these forces is carried out on a model - a support, the shape of which is shown in Figure 1. It is a simple beam loaded with an equally divided load $q$. It is assumed that the thickness of the support is small and therefore its stress is flat.