GMC Yukon 2012 Owner's Manual page 121

are using a single tether,
route the tether over the
seatback.
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 an adjustable headrest
or head restraint and you
are using a single tether,
raise the headrest or head
restraint and route the
tether under the headrest or
head restraint and in
between the headrest or
head restraint posts.
Seats and Restraints
If the position you are using
has a fixed headrest or
head restraint and you are
using a single tether, route
the tether around the
inboard or outboard side of
the headrest or head
restraint.
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