What should not be done when installing a child safety seat?

Allowing the safety seat to move more than one inch side to side compromises its effectiveness in a collision. A correctly installed child safety seat should be secured tightly to minimize movement, as excessive movement can increase the risk of injury to the child in an accident. The objective is to keep the seat securely anchored so that it remains in place during a crash, providing the intended protection.

The other options reflect best practices for installing a child safety seat. Securing the seat tightly is essential for safety, as is checking for compatibility with the vehicle. Using the LATCH (Lower Anchors and Tethers for Children) system guidelines is also crucial, as it provides specific instructions on how to properly install the seat using these additional anchors. Thus, the only appropriate response regarding what should not be done in the installation of a child safety seat is allowing it to move excessively side to side.