| 摘要 |
A concrete block comprising a front face having a height H1 and a width L1. A lip disposed underneath the front have having a height H2. A rear face having a height H3 and a width L2, wherein the rear face is shorter than the sum of H1 plus H2 by an amount H4, and wherein the sum of H1 plus H2 equals the sum of H3 plus H4. An upper surface forming a channel.
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