From the website
"Jamar Park Lok, Temporary Hydraulic Holding Brake, PK1 is a hydraulic line lock which uses the pressure from the brake system to hold your brakes locked. Step on the brake pedal, push the Park-Lok down, let off brake pedal, and it's locked. To release simply press on the brake pedal again and it opens automatically. Designed to hold your buggy stationary, and is great for holding vehicle in place while transporting on the trailer to eliminate pounding on transmission ring & pinion. DOT 3 Compatible!"
"Jamar Park Lok, Temporary Hydraulic Holding Brake, PK1 is a hydraulic line lock which uses the pressure from the brake system to hold your brakes locked. Step on the brake pedal, push the Park-Lok down, let off brake pedal, and it's locked. To release simply press on the brake pedal again and it opens automatically. Designed to hold your buggy stationary, and is great for holding vehicle in place while transporting on the trailer to eliminate pounding on transmission ring & pinion. DOT 3 Compatible!"