at the top face 26 and a lower opening not shown at the bottom face 28 the portion of the block between the side walls 22 and the channel 24 is a shear supporting portion 25 in use a retaining wall 40 as shown in fig2 is constructed from a plurality of masonry blocks 10 the wall is constructed by laying the masonry blocks 10 in a plurality of courses 42 the blocks are layed such that the front faces 12 of the blocks 10 are substantially co planar as are the back walls 16 the back walls 16 combine to form a rear face 44 of the retaining wall 40 each course 42 is offset from an adjacent course 42 by 50 in this way the extension portion 18 of a first block 10 a in a first course 42 a is adjacent a portion 16 a of the back wall 16 of an adjacent second block 10 b and adjacent a portion 16 b of the back wall 16 of an adjacent third block 10 c the second and third blocks 10 b 10 c being in a second course 42 b it will thus be apparent that the lower opening of the channel 24 of the first block 10 a locates outside the back wall 16 of the adjacent blocks 10 b 10 c and is thus accessible even after subsequent courses 42 have been laid once the retaining wall has been constructed as shown in fig2 it is possible to introduce soil reinforcing members in the forms of strips 46 of geo grid material into the.