The ornamental design for a screwnail, as shown and described.
FIG. 1 is a front elevational view of the screw nail;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a left-side elevational view thereof;
FIG. 4 is a right-side elevational view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof; and,
FIG. 7 is a cross-sectional view thereof taken along line 7-7 in FIG. 1.
The dot-dash chain lines indicates a boundary of the claimed subject matter and form no part of the claimed design. The broken lines depict environmental subject matter only and form no part of the claimed design.