The ornamental design for a rackholder, as shown and described.
FIG. 1 is a top, front, and right side perspective view of a rack holder showing our new design;
FIG. 2 is an additional top, front, and right side perspective view thereof;
FIG. 3 is a bottom, front, and left side perspective view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken-line disclosure in the views is understood to represent both environmental structure provided for illustrative purposes only and portions of the rack base which form no part of the claimed design. In addition, the broken lines which lie adjacent to the claimed area shown with surface shading are understood to represent unclaimed boundaries between claimed and unclaimed elements.