2003 GMC Yukon Owner's Manual - Page 75

5. Pull the rest of the shoulder belt all the way out of the retractor to set the lock. 6. To tighten the belt, feed the shoulder belt back into the retractor while you push down on the child restraint. You may find it helpful to use your knee to push down on the child restraint as you tighten the belt. You should not be able to pull more of the belt out of the retractor once the lock has been set. 7. Push and pull the child restraint in different directions to be sure it is secure. 1-69