Air Brake Foot Valves
Foot valves are attached to the brake pedal. This is the valve that actually starts the process of a brake application when you step on the brake pedal. Your foot valve may be mounted to the inside or outside of the firewall, or it may be mounted under the floor of the cab.
Replacement foot valves, or treadle valves, are sold as just the basic valve with no pedal attached. Treadle assemblies can be special ordered when needed.