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: Rear brake (disc) inspection
Brake Judder Repair Hint
1. (See FRONT BRAKE (DISC) INSPECTION.)
Disc Plate Thickness Inspection
Caution
Excessive runout may result if the disc plate is removed from the
vehicle then machined. Machine the disc plate while installed on the
vehicle.
1. Measure the thickness of the dis ...
Mazda 6 Owners Manual: No.8 no cool air
When performing an asterisked (*) troubleshooting inspection, shake the
wiring harness and connectors while performing the inspection to discover
whether poor contact points are the cause of any intermittent malfunctions.
If there is a problem, check to make sure connectors, terminals ...