Abstract: A plurality of walls are interconnected to form a hollow construction block including top and bottom contiguous block joining structure. The top contiguous block joining structure includes a first closed geometric shape adjacent to a second closed geometric shape. The first and second geometric shapes protrude above the side walls and have a width less than the width of the overall block and a combined length less than the length of the block. The bottom contiguous block joining structure includes a recess dimensioned to receive a joining structure dimensioned identically to the top contiguous block joining structure.