Tesla MODEL X 2015 Owner's Manual page 52

Seating Children Safely
Single Strap - Second Row Monopost Seats:
For single-strap tethers, position the strap in the
outboard seating positions over the outside-facing side
of the head restraint (the same side of the head restraint
as the seat belt retraction mechanism). In the center
seating position (if equipped), center and position the
strap over the top of the head restraint.
Single Strap - Second Row Bench Seats:
50
For single-strap tethers, position the strap in the
outboard seating positions over the outside-facing side
of the head restraint (the same side of the head restraint
as the seat belt retraction mechanism). In the center
seating position (if equipped), center and position the
strap over the top of the head restraint.
MODEL X Owner's Manual