is located substantially centrally with respect to the front and rear faces 7 8 and the end faces 20 22 of the wall portion 2 in other embodiments the apertures 6 6 u2032 may not be located in the centre of the wall portion 2 however preferably the apertures 6 6 u2032 are vertically aligned with each other when the well section is standing in an upright position the aperture 6 u2032 is the lower connecting portion 10 provides a path between the upper and lower cavities 4 5 the importance of which will be described later the wall section 1 is precast from concrete using a mould in a manner which is well known in the art in some cases it may be advantageous to precast the wall section 1 having solid connecting portions 9 10 and then drill through these connecting portions to form the apertures 6 6 u2032 in a method of building a free standing wall a number of wall sections 1 are placed side by side such that their respective end faces 20 22 are in contact and their respective front and rear face portions 7 8 are aligned once all of the required wall sections 1 have been placed in their correct positions concrete is poured through each of the apertures 6 in the top connecting portions 9 of one or more sections 1 the concrete flows through the aperture 6 into the upper cavity 4 and is then able to flow through the aperture 6 u2032 in the second connecting portion 10 and into the lower cavity 5 because the ends 14 15 of the cavities 4 5 are open concrete is able to flow through into an aligned cavity 4.