Toyota 2009 Tundra Owner's Manual page 185

1-7. Safety information
Child restraint systems with a top tether strap (Double Cab models)
Right rear seat or center rear seat
n
158
Replace the head restraint.
Installing position:
Right side passenger seat
Center passenger seat (Bench
type seat)
Raise the head restraints of right
and center seats.
Pull up the straps of right and
center seats.