The ornamental design for a toolholder, as shown and described.
FIG. 1 is the perspective view of a tool holder showing the new design;
FIG. 2 is a front side view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken line showing the attachment mechanism, indicated by a first broken line, and the stitching, indicated by a second broken line are for the purpose of showing environmental structure and forms no part of the claimed design.