The ornamental design for a drywallpatchbackingstem, as shown and described.
FIG. 1 is a top, perspective view for a drywall patch backing stem showing my new design;
FIG. 2 is a right side view thereof, the left side, the front side and rear side view being the same image thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof;
FIG. 5 is a sectional view taken along lines 5-5 from FIG. 2 thereof;
FIG. 6 is a sectional view taken along lines 6-6 from FIG. 2 thereof; and,
FIG. 7 is a sectional view taken along lines 7-7 from FIG. 2 thereof.
The broken lines in FIGS. 1, 2, and 5 show the a drywall patch backing stem to indicate that no particular length of the drywall patch backing stem forms a part of the claimed design.
The claimed design is broken in the center to indicate indefinite length.