The ornamental design for a treestud for mounting an electrical box, as shown and described.
FIG. 1 is a an isometric view of a tree stud for mounting an electrical box;
FIG. 2 is a side elevation view of the tree stud rotated thirty (30) degrees about its longitudinal axis from the orientation illustrated in FIG. 1;
FIG. 3 is a side elevation view of the tree stud in its orientation illustrated in FIG. 1;
FIG. 4 is a end elevation view of the tree stud taken from the right side of FIG. 3;
FIG. 5 is a end elevation view of the tree stud taken from the left end of FIG. 3; and,
FIG. 6 illustrates two the tree studs inserted through holes in upper and lower flanges of an electrical box and secured thereto with hexagonal nuts, said electrical box and hexagonal nuts illustrated in phantom lines forming no part of the claimed design.