These locks are intended to help prevent children from accidentally opening the rear doors. Use them on both rear doors whenever a child rides in the rear seat of the vehicle.
If you slide the child safety lock to the lock position before closing that door, the door cannot be opened from the inside. The door can only be opened by pulling the outside handle.

Locking, Unlocking with Door- Lock Knob
Trunk LidMazda 6 Owners Manual: Shroud panel removal/installation
1. Remove the bonnet. (See BONNET REMOVAL/INSTALLATION.)
2. Remove the front bumper. (See FRONT BUMPER REMOVAL/INSTALLATION.)
3. Remove the front combination light. (See FRONT COMBINATION LIGHT
REMOVAL/INSTALLATION.)
4. Remove the front bumper reinforcement. (See BUMPER REINFORCEMENT
REMOVAL/ ...
Mazda 6 Owners Manual: Fuel-Filler Lid and Cap
WARNING
When removing the fuel-filler cap, loosen the cap slightly and wait for
any hissing to stop, then remove it: Fuel spray is dangerous. Fuel can burn
skin and eyes and cause illness if ingested. Fuel spray is released when there is
pressure in the fuel tank and the fuel-filler cap is re ...