The ornamental design for a stay for furniture, as shown and described.
FIG. 1 is a perspective view of the front, left and top of a stay for furniture showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a left side view thereof;
FIG. 7 is right side view thereof;
FIG. 8 is an enlarged left side view thereof; and,
FIG. 9 is an enlarged right side view thereof.
The broken lines shown in the drawings are for the purpose of illustrating unclaimed portions of the stay for furniture and form no part of the claimed design.