Patent ID: 8464481

Claim:
A corner block having spaced-apart front and rear sections interconnected by two laterally spaced-apart side sections that jointly define an internal cavity that extends completely through the block from a top face thereof to a bottom face thereof, an upper protrusion protruding upwardly from the top face of the rear section rearward of the cavity, and two lower protrusions protruding from a wall of the cavity into the cavity at a bottom portion of the block, the two lower protrusions being spaced apart to define a gap therebetween, and the upper protrusion being located and dimensioned relative to the two lower protrusions so that two corner blocks that are mirror images of one another can be stacked one atop the other with the upper corner block rotated 90 degrees relative to the lower corner block and the upper protrusion of the lower corner block fitted into the gap between the two lower protrusions of the upper corner block to interlock the upper and lower corner blocks.