FORD 2013 E-450 v.3 - Manual (Page 24)

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.
Child Safety 23
2013 Econoline (eco)
Owners Guide gf, 3rd Printing, May 2013
USA (fus)