I claim the ornamental design for a paving block, as shown and described.
FIG. 1 is a perspective view of a paving block showing my new design;
FIG. 2 is a top view of the paving block of FIG. 1;
FIG. 3 is a front view of the paving block of FIG. 1;
FIG. 4 is a right side view of the paving block of FIG. 1;
FIG. 5 is a rear view of the paving block of FIG. 1;
FIG. 6 is a left side view of the paving block of FIG. 1; and,
FIG. 7 is a top view of the paving block of FIG. 1 with its environment shown in broken lines.
The broken lines in all drawing views are included for the purpose of illustrating portions of the paving block that form no part of the claimed design. The broken line showing of the like paving blocks in FIG. 7 view represents environmental subject matter. None of the broken lines form a part of the claimed design.