The ornamental design for a thumbscrewadjuster for a weight distribution hitch, as shown and described.
FIG. 1 is a front, top right perspective view of a thumbscrew adjuster for a weight distribution hitch with thumbscrew adjuster uninstalled according to the invention;
FIG. 2 is a front, top right perspective view of a thumbscrew adjuster for a weight distribution hitch with thumbscrew adjuster installed according to the invention;
FIG. 3 is a front elevational view of FIG. 2 according to the invention;
FIG. 4 is a rear elevational view of FIG. 2 according to the invention;
FIG. 5 is a top plan view of FIG. 2 according to the invention;
FIG. 6 is a bottom plan view of FIG. 2 according to the invention; and,
FIG. 7 is a left elevational view of FIG. 2 according to the invention with the right elevational view being a mirror image thereof.
The broken line showing of the slot and holes in FIGS. 1, 2 and 7 is included for the purpose of illustrating environmental use only and forms no part of the claimed design.