The theory of elasticity has been a well-established domain of engineering science for over a century, and solutions exist for many particular problems. It is not the aim of this contribution to extend the scope of the theory, but instead to draw attention to a specific way to formulate problems. So this contribution touches upon didactics in mechanics or, if you like, systematics; one may regard it as an educational section in a valedictory volume dedicated to a devoted teacher.Civil Engineering and Geoscience