The ornamental design for a block for a retainingwall, as shown and described.
FIG. 1 is a front perspective view of a block for a retaining wall.
FIG. 2 is a front elevational view of the block for a retaining wall of FIG. 1.
FIG. 3 is a rear elevational view of the block for a retaining wall of FIG. 1.
FIG. 4 is a right side elevational view of the block for a retaining wall of FIG. 1.
FIG. 5 is a left side elevational view of the block for a retaining wall of FIG. 1.
FIG. 6 is a top plan view of the block for a retaining wall of FIG. 1.
FIG. 7 is a bottom plan view of the block for a retaining wall of FIG. 1; and,
FIG. 8 is a front perspective view of a retaining wall, shown in broken lines, including the block for a retaining wall of FIG. 1. The broken lines depict environment that forms no part of the claimed design.
The broken lines in the drawings depict portions of the block for a retaining wall that form no part of the claimed design.