Backrest

FIG. 1 is a front elevation view of a backrest showing the new design;

FIG. 2 is a rear elevation view thereof;

FIG. 3 is a left side elevation view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a perspective view thereof.

The broken lines shown in the drawings illustrate portions of the article that form no part of the claimed design.