An assembly includes a rocker elongated along a vehicle longitudinal axis. A first slider is supported by the rocker. A second slider is supported by the rocker and is spaced from the first slider along the longitudinal axis. A first actuator is configured to slide the first slider relative to the rocker along a lateral axis. A second actuator is configured to slide the second slider relative to the rocker along the lateral axis. A cable extends from the first slider to the second slider.