Buick Lucerne 2007 Owner's Manual page 44

Q:
What if a child is wearing a lap-shoulder
belt, but the child is so small that the
shoulder belt is very close to the child's
face or neck?
A:
If the child is sitting in a seat next to a window,
move the child toward the center of the vehicle.
Also see Rear Safety Belt Comfort Guides on
page 39. If the child is sitting in the center rear
seat passenger position, move the child toward
the safety belt buckle. In either case, be sure
that the shoulder belt still is on the child's
shoulder, so that in a crash the child's upper
body would have the restraint that belts
provide.
44
CAUTION:
{
Never do this.
Here a child is sitting in a seat that has a
lap-shoulder belt, but the shoulder part is
behind the child. If the child wears the
belt in this way, in a crash the child might
slide under the belt. The belt's force
would then be applied right on the child's
abdomen. That could cause serious or
fatal injuries.