The ornamental design for a backrest for bleacherseats, as shown and described.
FIG. 1 is a front perspective view of a backrest for bleacher seats showing
my new design, the fragmentary seat depicted by means of broken lines
being shown for illustrative purposes only and forming no part of the
claimed design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a side elevational view taken from the right side of FIG. 2, the
left side view being a mirror image thereof;