Loose harnesses are a very common occurrence, but in order to properly secure our child we need to know how to tighten them correctly. A loose harness strap may cause your child to move out of a secure position. In a case of a crash that could lead to serious injury or even the child's ejection from the child seat. In order to prevent that from happening, you should always remember the “Pinch test” while securing your child in the seat. When your child is buckled in, place your thumb and pointer finger on the harness at your child’s collarbone. Place the two fingers apart and try to “pinch” a larger area on the harness. If you are able to get any amount of the strap between your fingers that indicates that the strap you are pinching is too loose.
At the same time please take into account that the harness should not be too tight, either. The strap should not push your child’s body into un-natural positions or place pressure on the flesh, but should instead lie in a relatively straight line and not cause the child any discomfort.