This electronic valve sits in the front brake circuit and keeps the front calipers clamped shut after the driver releases the brake pedal. It allows the rear wheels to spin freely without fighting the rear brakes, making it essential for heating up drag tires in the burnout box. Once the switch is released, normal braking function returns.
Heard on the job
Hit the line lock, dump the clutch, and let it eat until you see smoke in the mirrors.
Insider tip
Drag racers use this to avoid cooking their rear brake pads while warming up their slicks.