Diono mXT Instruction Manual page 11

Proper Positioning on Vehicle Seat
Place booster seat on vehicle seat so it is resting firmly on vehicle seat
bottom and touching the vehicle seat back. (Fig. 3)
IMPORTANT:
When using the booster seat, try to position backrest in full
contact with vehicle seat back. (Fig. 3)
Securing the Child
1) Make sure booster seat is properly positioned and installed on vehicle
seat as per the instructions.
2) Properly position child: sitting upright and all the way back in the
booster seat.
3) Make sure booster seat backrest width is adjusted to narrowest width
setting that comfortably fits child. (Fig. 5)
4) Raise the headrest to access upper belt guides. (Fig. 4) Feed the diagonal
portion of the seatbelt through the upper belt guide on the side
opposite the seatbelt buckle.
(Fig. 6)
5) Fasten seatbelt across child: Lap portion of seatbelt should rest within
both red lower belt guides. Diagonal shoulder portion should route
inside the red lower belt guide closest to the buckle and over child's
shoulder.
6) Adjust headrest to proper height (Fig. 4): Upper shoulder guide should
be slightly above (at least 1 cm) the child's shoulders. (Fig. 7)
WARNING:
If headrest is adjusted to maximum height and child's shoulder
height is closer than 1 cm to the upper belt guide, child is too tall for booster.
7) Make sure seat belt is not twisted and lays flat across child's lap, torso
and shoulder. (Fig. 6)
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