2009 Buick Lucerne Owner's Manual - Page 58

If the position you are using does not have a headrest or head restraint and you are using a dual tether, route the tether over the seatback. If the position you are using has a fixed headrest or head restraint and you are using a dual tether, route the tether around the headrest or head restraint. If the position you are using has a fixed headrest or head restraint and you are using a single tether, route the tether over the headrest or head restraint. 3. Push and pull the child restraint in different directions to be sure it is secure. 1-54