The ornamental design for an external cornermaterial for walls, as shown and described.
FIG. 1 is a front view of an external corner material for walls showing my new design;
FIG. 2 is a back view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a left side view thereto;
FIG. 7 is a front, top perspective view thereof; and,
FIG. 8 is a back, bottom perspective view thereof.
The break lines at a middle portion in FIGS. 1, 2 and 5-8 depict the boundaries of the claim. The area between the break lines at the middle portion in FIGS. 1, 2 and 5-8 forms no part of the claimed design.
The remaining broken lines depict portions of the external corner material for walls that form no part of the claimed design.