To check if your car seat is installed tightly enough you should hold the seat in the area of the seat belt or latch belt path and try to move it from side to side across the vehicle seat. The car seat should not move more than one inch from side to side. (Movement in the front area of the seat is OK.) If you are using a seat belt to install your car seat it needs to be "locked" to prevent it from loosening as you drive. Some lap and shoulder seatbelts are "switchable". If you slowly pull the belt all the way out to the end it switches over to a locked mode which prevents slack from entering the belt path. If your seatbelt is not switchable you will need to use a locking clip. The locking clip holds the shoulder portion and lap portion of the belt together and should be approximately one inch from the buckle. It is recommended that you periodically check the tightness of your seat to insure that it hasn't loosened or that someone hasn't inadvertently unbuckled the seatbelt. Note
: Please refer to your vehicle manual and child restraint manual for specific instructions.
Securing a Child in a Safety Seat
Harnesses need to be very snug on a child. One finger should fit snugly between the harness and the child's collar bone. If you can pinch any slack in the harness then it is too loose. Harness tightness can be equated to a watch band or a belt worn to hold up pants - comfortable yet snug enough to stay in place and be functional. The harness clip should be positioned across the center of the child's chest at armpit level. This clip holds the harnesses in position on the child's shoulders. If this clip is too low then the harnesses could potentially slip off the child's shoulders and the child could be thrown out of the seat in a crash.
It is recommended that children wear only thin layers of clothing when secured in a car seat. Basically you want the least amount of material between the car seat, the child, and the harnesses. Once the child is secured snugly in the harness system blankets can be placed over the child for warmth. Thick winter coats and snow suits are particularly discouraged because it is difficult to get a snug fit with the harnesses, and the material can compress under the harnesses in a crash causing the child to be thrown from the seat. After market buntings sold for infants that are placed under and around the child and harness system are also discouraged for similar reasons. You can purchase bunting type covers that are placed on the top of the seat once the child is properly secured.