The ornamental design for sign holder, as shown and described.
FIG. 1 is a front perspective view of a sign holder showing my new design,
with the post broken away in the center to indicate indeterminate length,
and with the broken line showing for illustrative purposes only and
forming no part of the claimed design;
FIG. 2 is a cross-sectional view looking in the direction of lines 2--2 of
FIG. 3;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a cross-sectional view looking in the direction of lines 4--4 of
FIG. 3; and,