What type of transverse connection on round ductwork uses a rolled angle iron flange with matching bolt holes?

The correct choice is made because a companion flange is specifically designed to create a strong, secure connection between two sections of round ductwork. This type of connection typically employs a rolled angle iron flange, which not only enhances stability but also features matching bolt holes that facilitate straightforward assembly. This design provides a durable seal and ensures that the ductwork maintains its integrity under various airflow conditions.

In contrast, the other options represent different types of connections used in ductwork but do not specifically utilize the rolled angle iron flange configuration. For example, swedge flanges are a simpler mechanical connection that relies on interlocking designs rather than a bolted design, while TDC/TDF flanges involve a different construction method using flanged edges and may include a flat or folded edge. Capped standing refers to a different approach of terminating ductwork without a connection focus similar to that of a companion flange, making it unsuitable for this specific type of joint.