They allow airflow to go in a single course and to circumvent it in the other course. They are really constructed from corrosion resistant extruded aluminum. The vertical blade configuration allows for the actuator to be mounted down below the damper and is particularly perfect for applications where base accessibility https://dampersforindustrialsecto34556.ziblogs.com/37258970/the-definitive-guide-to-heavy-duty-stainless-steel-damper-manufacturers