Chevrolet Suburban 2007 Owner's Manual page 74

Top Tether Anchor
A top tether (A, C) anchors the top of the child
restraint to the vehicle. A top tether anchor is built
into the vehicle. The top tether attachment (B)
on the child restraint connects to the top tether
anchor in the vehicle in order to reduce the forward
movement and rotation of the child restraint
during driving or in a crash.
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Your child restraint may have a single tether (A)
or a dual tether (C). Either will have a single
attachment (B) to secure the top tether to
the anchor.
Some child restraints with top tethers are designed
for use with or without the top tether being
attached. Others require the top tether always to
be attached. In Canada, the law requires that
forward-facing child restraints have a top tether,
and that the tether be attached. In the United
States, some child restraints also have a
top tether. Be sure to read and follow the
instructions for your child restraint.
If the child restraint does not have a top tether,
one can be obtained, in kit form, for many
child restraints. Ask the child restraint
manufacturer whether or not a kit is available.