A flange is a mechanical component used to join sections of ductwork together in heating, ventilation, and air conditioning (HVAC) systems. It is designed to create a secure, airtight seal between ducts, which helps to ensure that air flows efficiently through the system without leakage. The flange typically features pre-drilled holes for bolting or screwing the duct sections together, providing a stable and tight connection. This component plays a crucial role in maintaining the performance and energy efficiency of the HVAC system by preventing air loss and ensuring proper pressure and airflow.