The ornamental design for a temporary coversheet for a window frame opening, as shown and described.
FIG. 1 is a front elevational view of a cover sheet for a window frame opening, showing my new design;
FIG. 2 is an edge view of the cover sheet of FIG. 1 placed over a window frame, the broken line disclosure of a portion of a window frame and window being for illustrative purposes only and understood to form no part of the claimed design;
FIG. 3 is a front elevation view of the cover sheet in accordance with another embodiment of my new design; and,
FIG. 4 is an edge view of the cover sheet of FIG. 3 placed over a window frame, the broken line disclosure of a portion of a window frame and window being for illustrative purposes only and understood to form no part of the claimed design.
The solid black coloring shown in the drawings represents color cotrast.