FIG. 1 is a front perspective view of a dock insert showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is a bottom plan view thereof;

FIG. 8 is another front perspective view thereof showing the design in combination with an environment in which the design may be used; and,

FIG. 9 is another perspective view thereof.

The broken lines in the Figures are for illustrative purposes only and form no part of the claimed design.