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: Parking brake (lever type) removal/installation
1. Remove the center console. (See CONSOLE REMOVAL/INSTALLATION.)
2. Remove the rear seat cushion (4SD) or rear seat (5HB) . (See REAR SEAT
REMOVAL/
INSTALLATION.)
3. Remove the exhaust pipe bracket.
4. Remove in the order indicated in the table.
5. Install in the reverse order of removal.
6 ...
Mazda 6 Owners Manual: General procedures
PRECAUTION (SUSPENSION)
Wheels and Tires Removal/Installation
When a wheel is installed, tighten it to 88-118 N·m {9.0-12.0 kgf·m,
65.0-87.0 ft·lbf}.
Suspension Links Removal/Installation
Tighten any part of the suspension that uses rubber bushings only after the
vehicle has been lowered ...