What is the notch on couplings that aids in connecting the two ends called?

The notch on couplings that aids in connecting two ends is referred to as the Higbee indicator. This feature is specifically designed to ensure that the male and female pieces of the coupling align correctly when being connected. The indicator helps firefighters quickly and efficiently couple hoses under pressure or in emergency situations, reducing the chance of error and ensuring a secure connection.

In the context of firefighting operations, the proper alignment of couplings is crucial for maintaining the integrity of water supply lines and ensuring that no leaks occur during use. The Higbee indicator serves an essential function by allowing firefighters to quickly identify the correct orientation for coupling the hoses, thereby improving response times and safety during an operation.