Distribution function seems be the most full analytical description of any stochastic process. Distribution function for multiple Coulomb scattering for infinite and uniform medium had been obtained at the first half of the last century. We have used it successfully for the dynamics exploration of the beam crossing thin foil normally to its surface. The function mentioned cannot be used directly for the case of the foil installed at some angle to the beam direction of propagation. In mathematical sense, this case is already new problem and new analytical solution is required. To find out the analytical solution for this case, partial differential equation with appropriate boundary conditions must be solved. As it takes place for the majorities of the mathematical physics problems, the exact analytical solution in this specific case is unavailable. We tried to find a different approach searching for approximate solution of boundary problem based on exact solution for infinite scattering. The paper describes the flow lines model for multiple Coulomb scattering that results in analytical explanations of different phenomena taking place in the case of beam incline incidence on the border separating vacuum and scattering medium.