Abstract: A wall having an outer structural component of masonry units which are provided with dovetail slots in their inner faces. A fixing device is provided which has a tongue at one end of a screw threaded rod and an adjustable cap at the other. The tongue is inserted and fixed into the dovetail slot and the cap adjusted by screwing on the rod. Caps of the various fixing devices are aligned in a vertical plane and an inner skin of plaster board or the like secured by screwing to the aligned caps. Transfer of moisture from the porous masonry wall to the inner skin is prevented by providing sufficient screw threading on the rod to allow a number of turns of the thread to remain exposed when the cap is screwed to its innermost position.