The two most popular ways to mount the door closer are either standard (regular) arm or parallel (pa) arm. The standard arm closer always mounts on the pull side of the door, so it would never be used on exterior outswing doors. It has a better power efficiency than the PA arm, but the arm projects out from the door. The parallel arm closer always mounts on the push side of the door. While it is not quite as strong as the standard arm mount, it is still plenty strong enough for most applications and it looks better as the arm lays parallel with the door in the closed position.