Lincoln 2011 MKX Owner's Manual page 172

Seating and Safety Restraints
Children and booster seats vary in size and shape. Choose a booster that
keeps the lap belt low and snug across the hips, never up across the
stomach, and lets you adjust the shoulder belt to cross the chest and
rest snugly near the center of the shoulder. The drawings below compare
the ideal fit (center) to a shoulder belt uncomfortably close to the neck
and a shoulder belt that could slip off the shoulder. The drawings below
also show how the lap belt should be low and snug across the child's
hips.
If the booster seat slides on the vehicle seat, placing a rubberized mesh
sold as shelf or carpet liner under the booster seat may improve this
condition. Do not introduce any item thicker than this under the booster
seat. Check with the booster seat manufacturer's instructions.
171
2011 MKX (mkx)
Owners Guide, 2nd Printing
USA (fus)