Abstract: A wall in which hollow units analogous to blocks are built up in overlapping superimposed courses, each unit having two spaced parallel vertical panels of skins of rectangular form, the units being held by concealed fastening members; characterized in that each panel has edge grooves extending along its upper and lower horizontal surfaces to be contiguous with those of adjacent panels, and each fastening member has a body portion to extend between spaced panels, the ends of the body portion each having hook portions extending upwards and downwards respectively into adjacent grooves of the panel edges, while said body portion between adjacent panels has two upper lugs extending into contact with respective upper panels, and two lower lugs extending down and into contact with respective spaced lower panels, the fastening member, constituting a one piece connector and spacing member.