The ornamental design for an extension handle for a wrench, as shown and described.
FIG. 1 is a front elevation view of an extension handle for a wrench showing my new design, the opposite side being a mirror image of the shown;
FIG. 2 is a left side elevation view thereof;
FIG. 3 is a right side elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is an isometric view thereof; and,
FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 4.
The broken lines in FIG. 6 of the drawings depict a combination end wrench as environmental subject matter only and form no part of the claimed design.