Abstract: An interlocking system of blocks comprises a basic block having side walls and transverse webs all of constant thickness with the webs being rectangular in shape and offset upwardly from the bottom of the edges of the side walls to form recesses at the bottom and projecting portions at the top which interlock with the next adjacent upper row. The webs are spaced equidistantly along the block with the end most webs spaced from the ends of the blocks by one half of the spacing. Corner blocks are formed so that the web at the end of the block has an outer face coincident with the end face of the block and a recess in the lower edge of each of the side walls. The blocks are simple to manufacture, resistant to damage and easily assembled.