www.GeneralLock.com C9000 Series Door Closer Installation Parallel Arm and 9016 DP-18PA Drop Plate Installation Parallel Arm installation: . Parallel arm application is the least power efficient. It provides approximately 25% less power than regular arm. It is installed on the frame stop (push) side of the door. Since it is parallel with the door, it is chosen for appearances and is least susceptible to vandalism, making it a popular choice in schools.