This brake lock using hydraulic line pressure hold your brakes. For cars, trucks, Disc or Drum brakes.Operation: 1) step on the brakes. 2) push down the knob on the Brake Lock. 3) Release the foot brake and it’s locked. 4) To release the lock, step on the foot brake and it opens automatically. Install: 1) Use two holes to mount the brake lock where is properly. 2) In port (1/8” NPT): connect to master brake cylinder, it also come with 3/16” brake line fitting, you can chose to use the fitting or not. 3) Out port (1/8” NPT): connect to rear brakes. , it also come with 3/16” brake line fitting., you can chose to use the fitting or not. Dimensions: 2” x 1.5” x 1” Note: it should NOT be used under unintended, emergency or long time hold brake. Package: 1x Sanding Disc