The ornamental design for a bathtubsidewall channelling, as shown and described.
FIG. 1 is a side elevation view of a bathtub sidewall channeling showing my
new design, it being understood the opposite side is a mirror image
thereof;
FIG. 2 is an end view of FIG. 1;
FIG. 3 is an opposed end view of FIG. 1; and,
FIG. 4 is a bottom view of FIG. 1.
The broken line shown in the drawing is for illustrative purposes only and
forms no part of the claimed design.