Ford E 2013 Series Owner's Manual page 24

Child Safety
23
If the booster seat slides on the vehicle seat upon which it is being used,
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.
2013 Econoline (eco)
Owners Guide gf, 3rd Printing, May 2013
USA (fus)