The rear armrest in the center of the rear seatback can be used (no occupant in the center seat) or placed upright.

WARNING
Never put your hands and fingers around the moving parts of the seat and armrest:
Putting your hands and fingers around the moving parts of the seat and armrest is dangerous as they could get injured.
Split Folding
Head RestraintsMazda 6 Owners Manual: Roof molding installation
1. Attach the roof molding to the T stud at the A section.
2. Press in the roof molding along the direction (1) shown in the figure and
attach it to the clip A at the B section.
3. Hook the roof molding to the clip B at the C section, press it in, and
attach the roof molding to the clip B.
...
Mazda 6 Owners Manual: Precaution
Vehicles with ABS/TCS
1. The ABS warning light, BRAKE system warning light, TCS indicator light
and/or TCS OFF light illuminate even when the system is normal.
*1 : In cases where the light may illuminate, only when ABS/TCS HU/CM detects
that speed sensor of rear wheel is malfunctioning.
*2 ...