Chevrolet 2002 Prizm Owner's Manual page 50

12. Now fasten the left and right halves of the shoulder
harness clip together. The purpose of this clip is
to help keep the harness positioned on the
child's shoulders.
1-44
CAUTION:
An unfastened shoulder harness clip won't help
keep the harness in place on the child's shoulders.
If the harness isn't on the child's shoulders, it
won't be able to restrain the child's upper body
in a sudden stop or crash. The child could be
seriously injured. Make sure the harness clip is
properly fastened.