The paper studies the stability of an elastic orthotropic rectangular cantilever plate under compressive forces applied to the face opposite to the seal. The aim of the study was to obtain the range of critical forces and the relevant shapes of the supercritical equilibrium. The deflection function was chosen as a sum of two hyperbolic-trigonometric series with the addition of special compensating terms for the free terms of the Fourier cosine series to the symmetric solution. For the square ribbed plate, the first three critical loads of the symmetric solution and the first critical load of the antisymmetric solution were obtained. The authors present 3D images of the respective equilibrium forms. The results of the study can be used to study the stability of cantilever elements of various structures.