The ornamental design for a painting-tool blade, as shown and described.
FIG. 1 is a top and left side perspective view of our design for a painting-tool blade;
FIG. 2 is a left side elevation view of the painting-tool blade of FIG. 1;
FIG. 3 is a right side elevation view of the painting-tool blade of FIG. 1;
FIG. 4 is a top elevation view of the painting-tool blade of FIG. 1; and,
FIG. 5 is a bottom elevation view of the painting-tool blade of FIG. 1.
The broken lines shown along portions of the blade in FIGS. 1-5 illustrate aspects of the blade that form no part of the claim, while the broken lines suggesting a handle in all figures are directed to environment that also forms no part of the claimed design.