There's three ports on a hill holder. One is for the line coming from the master cylinder. One is for the line going to the rear brakes. One is for the line going to the front brakes. I am running a dual master cylinder and am not running the front brake line from the hill holder. Does it matter (other than the port for the line going to the rear brakes) which port I use (upper or lower) for the line coming from the master cylinder?