- Harness too slack - You shouldn't be able to get more than two fingers between the harness and your child's chest.
- Wrong routing of the seat belt - Never try to guess how a car seat should be fitted. Instead, make sure you follow the car seat manufacturer's instructions faithfully.
- Seat belts not plugged in - It sounds crazy but it's amazing how often parents forget to do this - usually because they're juggling all sorts of things in their hands and in their minds. Don't forget, nimble little fingers can also release a buckle.
- Car seat too loose - If you grab the base and try to wiggle it, it should hardly move.
- Seat belt buckle resting on frame - Only the webbing (the material part) of the seat belt should touch the car seat frame. Otherwise you can get `buckle crunch", making the seat belt spring open in a crash.