grooves are such that a slight spacing 33 is provided between vertically disposed blocks 20 to insure proper alignment the spacing between the blocks varies between 0 to u215b u2033 according to block height error although may be substantially reduced to a spacing between 0 010 u2033 and 0 020 u2033 by grinding the block bottoms while grinding the v cuts referring now to fig3 the arrangement is disposed with the adjacent rows of building blocks located in a staggered relationship it will be noted that the upper building block 20 overlaps the junction of the lower building blocks 20 in fig4 there are shown in partial perspective two masonry walls constructed of building blocks 20 that include reinforcing steel rods 32 that are disposed in the longitudinal and transverse direction these rods are utilized to reinforce the structures and extend through the chambers 30 of the building block which will serve to conduct all utilities wiring ducts etc if desired reinforced concrete 34 is poured into the chambers there are also provided vertically extending reinforced concrete columns 36 at the bottom of fig4 there is also shown in perspective the connection between the concrete slab 38 and the building blocks 20 to provide for proper leveling of the building blocks there are located on the slab 38 leveling channels 40 these channels are secured to the blocks by leveling bar 42 and a rod as shown in section 45 in order to properly level the building blocks relative to the concrete slab.