What method is used to connect pipes or fittings that involves threads on the end of the pipe?

The method used to connect pipes or fittings with threads on the end of the pipe is a threaded connection. This type of connection is commonly employed in various piping systems because it allows for a secure mechanical join between two components. The threads create a tight fit when the pipes or fittings are twisted together, which helps prevent leaks under pressure.

Threaded connections are particularly useful in applications that require disassembly or maintenance, as they can be easily unscrewed and reconnected. This contrasts with other methods, such as compression fittings, which typically rely on pressure to create a seal without the need for threading, or joint sealing, which focuses on using sealants to ensure tightness without mechanical interlock. The loose connection choice does not describe a method that effectively secures pipes or fittings together. Hence, the threaded connection stands out as the appropriate and most practical choice for this question.