How did they join lead pipes?

Lead pipes were typically joined using a method called "soldering," where molten lead was applied to the joint to create a seal. This process involved heating the ends of the pipes and then melting lead to fill the gap between them, ensuring a watertight connection. Additionally, some joints were made using threaded fittings, where the pipes were screwed together. However, due to health concerns over lead exposure, the use of lead pipes has been largely phased out in modern Plumbing.