How do I check that the harness is tight enough on my child?

The harness is properly tightened when the strap lies in a relatively straight line without sagging and does not press on the child's flesh or push the child's body into an unnatural position. If you can pinch the strap at the child's shoulders, the harness is too loose. Pull the Harness Adjuster Strap slowly while holding the Chest Clip away from the child's neck to tighten, and position the Chest Clip at armpit level. (Page 94)