What are notches cut into coupling lugs called?

Notches cut into coupling lugs are known as Higbee indicators. These indicators serve a specific purpose in safety and operational efficiency in certain applications, particularly in the context of connecting equipment. The primary function of Higbee indicators is to ensure that couplings are properly aligned when being connected, thereby preventing potentially dangerous situations that may arise from improper connections.

Higbee indicators are designed in such a way that they facilitate an easy connection process, promoting users to confirm that connections are made correctly. This is crucial in many scenarios where secure attachments are necessary for safety reasons, especially in industries like firefighting or industrial machinery.

The other options listed do not reflect the correct terminology used in this context. Thread indicators, groove markers, and connection indicators do not specifically refer to the notches on coupling lugs, highlighting that “Higbee indicators” is indeed the precise terminology used in engineering and safety practices associated with coupling mechanisms.