This chapter focuses on the study of conduction problems in steady or stationary state. In these cases, temperature will not be a function of time, but it will nevertheless depend on the coordinates that define the position of a given point of the solid considered. Studying steady-state conduction is of particular importance for the engineer. While the single-layer wall represents an interesting practical case for the engineer, study of conduction through walls composed of several layers of different materials presents even greater importance. The study of conduction in cylindrical walls is of great importance, particularly since it allows the heat dissipations through these walls to be calculated. In industry, the people often encounter conduction through spherical walls, notably in storage reservoirs. The chapter presents a study of the problems with convective-type boundary conditions, for single-layer walls, cylindrical pipes and spherical walls, respectively.