Can be used for either parallel arm or top jamb applications. Unitrol arms combine the features of a double lever arm overhead door stop/holder with the backcheck feature of the door closer to reduce door stopping shock loads to a minimum. The Unitrol uses a compression Spring buffer at the soffit plate/arm shoe that will absorb 30 lbf. of force, 5° prior to the door’s dead stop. Coupled with the door closer’s backcheck feature, this arm provides the most controlled stop available with a surface door closer.