The ornamental design for a tonneaucover side-rail locking device, as shown and described.
FIG. 1 is a top view of an embodiment of a tonneau cover side-rail locking device. The broken-lines in the drawing illustrate portion of the tonneau cover side-rail locking device and form no part of the claimed design;
FIG. 2 is a bottom view of the tonneau cover side-rail locking device shown in FIG. 1;
FIG. 3 is a front view of the tonneau cover side-rail locking device shown in FIG. 1;
FIG. 4 is a rear view of the tonneau cover side-rail locking device shown in FIG. 1;
FIG. 5 is a left side view of the tonneau cover side-rail locking device shown in FIG. 1;
FIG. 6 is a right side view of the tonneau cover side-rail locking device shown in FIG. 1;
FIG. 7 is a perspective view of a smaller-scale version of the tonneau cover side-rail locking device shown in FIG. 1;
FIG. 8 is a perspective view of the tonneau cover side-rail locking device shown in FIG. 1, when being attached/locked to a side-rail system. The broken-line showing of the side-rail system illustrates the environment of the claimed design and form no part thereof; and,
FIG. 9 is a side view of the tonneau cover side-rail locking device shown in FIG. 1, when being attached/locked to a side-rail system. The broken-line showing of the side-rail system illustrates the environment of the claimed design and form no part thereof; all arranged in accordance to one embodiment of the present disclosure.