We claim the ornamental design for sign holder, as shown and described.
FIG. 1 is a perspective view of a sign holder, and
FIG. 2 is an enlarged fragmentary view of FIG. 1 showing a center portion and end portions for clarity of illustration.
FIG. 3 is a front side view of the article in FIG. 1.
FIG. 4 is a top view of the article in FIG. 1.
FIG. 5 is a bottom view of the article in FIG. 1.
FIG. 6 is a first end view of the article in FIG. 1.
The rear side view of the article in FIG. 1 is a mirror image of the front side view in FIG. 3, and the opposing end view is a mirror image of the first end view in FIG. 6.
FIG. 7 is a perspective view of the sign holder in FIG. 1 but further including in dashed lines as environment a cross bar and wires stored thereon.
FIG. 8 is a front side view of the article in FIG. 7.
FIG. 9 is a bottom view of the article in FIG. 7; and,
FIG. 10 is a first end view of the article in FIG. 7.
The rear side view of the article in FIG. 7 is a mirror image of the front side view in FIG. 8, and the opposing end view is a mirror image of the first end view in FIG. 10, and the top view is identical to FIG. 4.
The portions of the sign holder shown in broken lines form no part of the claimed design.