The instruction booklet is the most important part of a child's car seat, Plunket says.
Plunket and Horizons Regional Council with help from the police held child restraint stops around Whanganui on Tuesday ensuring each child-carrying vehicle had an appropriate car seat and that it was fitted correctly.
Horizons roadsafe co-ordinator Glenda Leitao said it was about using the seats right to ensure they were effective.
"It's not so much that people aren't using car restraint seats, it's that they're not fitted correctly," she said.
Mrs Leitao said nearly 70 per cent of seats are incorrectly fitted in some way.