Typical CMU block foundations are hollow... but not ours! We only offer CRETELOCK Foundation Wall Replacements. Which are proven to provide more support both horizontally and vertically than traditionally build CMU walls. After the footing is prepared and the first row of CMU blocks are laid into place a 1/2 in hole is drilled down into every other cell of the cinderblock and rebar is placed vertically. Then each cell of the CMU block is filled with High Strength 50,000 psi Concrete. Mortar is then laid to connect the new row of CMU block. As you know CMU blocks alternate from row to row which means that each and every part of the wall is tied together with rebarb and concrete...forming the CRETELOCK Foundation Wall!