Energy storage is still an expensive operation in the sense that apart from the store itself, it also includes components for collection, transfer and control of energy flows. An interesting and important improvement would be achieved if the boundary of the store allowed heat transfer between the energy source and the storing material whenever the temperature gradient were favourable and inhibited the heat losses whenever such a gradient were reversed; in other words, the walls of the store would behave as thermal rectifiers. In this work one presents the rectifying effect of a vertical parallelogramic cavity and its application to thermal rectifying walls which could be used in thermal stores. The operation of such walls depends on the enhancement or inhibition of natural convection heat transfer. Using a Mach-Zehnder interferometer front to back ratios of between two and three have been measured.